PLC控制系统外文翻译
PLC建筑电梯控制系统中英文对照外文翻译文献
(文档含英文原文和中文翻译)中英文对照外文翻译文献Application of PLC in the Elevator Control System ofIntelligence BuildingAbstract: The paper mainly discusses one subsystem of intelligence building system: the elevator control system. The PLC strong ability in interference and so on makes the elevator industry one after another to apply the PLC to the elevator control system in order to replace the relay being used in traditional elevator control system. The Application of PLC in the Elevator control system reduces the breakdown rate and efficiently improves the operating reliability of the elevator with safety .The structureof system is also simple and tightly packed.The working principle of the elevator control system is: The spot control information is send into the ＰＬＣfrom the customer input devices firstly, then the PLC control cabinet is required to send out the control signal to drive the equipments according to the system demands. The elevator can then proceed the homologous action according to the control request .The paper selectsＯＭＲＯＮcompany’s Ｃ200HE series PLC, introducing parts of signal hookup of the elevator control system and explaining the function of the control cabinet. Lastly the automation programming is introduced. Simulated experiments enunciates that the design method is viable. It can make the personnel of the industry management center to long-distance monitor and control the elevator in control center, to connect the elevator control system with intelligence building industry management system by Ethernet or special-purpose network such as Lon Works.The elevator working state can also be timely watched.These not only can realize scientific centralized management of the elevator, but also can lower the elevator maintenance cost etc. It is one of the developing direction of intelligence building elevator control system.Keywords: PLC; intelligence building; elevator control system; working principle; program designⅠ. IntroductionIn 1980s The first intelligence mansion had been completed in America, then intelligence building has been abroadly taken attentions by the whole world.The concept of intelligence building has been put different meanings along with the development of society. The early stage intelligence building had been thought that it is equal to the intelligent mansion, but now the intelligence building not only includes the intelligence mansions but also involves intelligence residential districts. This paper mainly discusses one subsystem of intelligence building system: the elevator control system.In intelligence residential districts the enterprise’s information managing system mainly takes charge of the things which related to the daily life, for examplesupervising the district equipments, managing vehicles, disposing critical situations and so on.The elevator supervising and control system is also necessary to the intelligence residential districts.How to make people feel safe ,stable and comfortable and how to save energy resources and protect environments and so on are the basic requirements to the elevator control system.PLC is a common industry control device.It is a special industry control computer which has the perfect function and simple frame. The PLC strong ability in interference and so on makes the elevator industry one after another to apply the PLC to the elevator control system, in order to replace the relay being used in traditional elevator control system. The Application of PLC in the elevator control system reduces the breakdown rate and efficiently improves the operating reliability of the elevator with safety. This paper mainly discusses the elevator control system’s working principles, the system’s software and hardware realization methods and so on.Ⅱ. The Working Principle of Elevator Control System In Fig. 1 the Hardware Structure Graph of Elevator Control System is presented.Fig. 1 The Hardware Structure Graph of Elevator Control SystemThe Working Principles of Elevator Control System are stated as follows: The spot control information is send into the PLC from the customer input devices firstly, then the PLC control cabinet is required to send out the control signal to drive the equipments according to the system demands. The elevator can then perform thehomologous action according to the control request. There are velocity feedback devices in system, which adopt measure velocity generators to provide the elevator velocities and generally are installed in the tail of tow motors .So this is a feedback control system, which can improve the system’s control precision.Ⅲ. The Hardware Configuration of Control System It is not necessary to do interface circuit in the elevator’s PLC control system.What we should do is to send the signals to PLC digital input terminals.The signals include inside and outside calling signals ,floor location inspecting signals , limiting location signals ,opening and shutdown the elevator door signals etc. The DC power which is provided to PLC can be used as indicator light power. The PLC output points can be directly used to control transduce rs for the purpose of electrical motor’s positive turn and reverse ,stop and control each segment velocity and so on .ＯＭＲＯＮcompany’s Ｃ200HE series PLC has been selected as major control configuration according to the input/output points and the length of user’s program. On the other hand we also consider that the system’s function can be expanded in the future .Ｃ200HE series PLC ,whose perfect function and strong reliability, can meet these demands at present.Moreover, input and output devices are needed in elevator control system, besides the PLC, system’s major control device.Part of signal hookups of the elevator electric control system is shown in Fig.2.The control cabinet is the control center, from which we can send out various control commands. The control cabinet often was installed in the elevator room .The electric devices and signal systems, for example the contactors, relays, capacitances, resistors, rectifiers and transformers etc., are centralized in the control cabinet. The Power of the control cabinet was imported from the chief power of the elevator room. This power was also introduced into control panel by soft cables and was linked with each control buttons. The power lines which was derived from control cabinet was delivered to tow electric motors. Others control lines and signal lines were separately sent to each floor junctionⅣ. Program designThe design includes two parts: hardware and software.The hardware design is the base of software. Considering that the control demands are relatively complex, we design the programs separately according to the control function. Furthermore, we follow the principle as follows: When the elevator is ascending, the ascending demands are prior to other demands; When the elevator is descending, the descending demands are prior to other demands. The Sequential Function Chart (SFC) is adopted during the boxes to form elevator’s executive circuitry design. It is a method specially used in industrial sequential control. The SFC method can describe the system’s working procedure in great detail. For example there is a three layers intelligence building. A subprogram, the calling from the third floor as elevator in the first floor, is shown in Fig. 3 with SFC.When all SFC are drawn and I/O address lists are presented, we can convert the SFC to Ladder Diagram (LD).Considering the strict demands for time and for locked each other ,we introduce working bits to remember working steps. We should write out the working bits control program, which can link together each step and make the previous step as the next step restriction condition. Thus the actual outputs are the logic combination of these working steps.Ⅴ. ConclusionThe system program has been debugged completely at present. Simulated experiment enunciates that the design method is viable. Application of PLC in the elevator control system is an effective method. It can make the personnel of the industry management center to long-distance monitor and control the elevator in control center, to connect the elevator control system with intelligence building industry management system by Ethernet or special-purpose network such as Lon Works. The elevator working state can also be timely watched. These not only can realize scientific centralized management of the elevator, but also can lower the elevator maintenance costs etc. It is one of the developing direction of intelligence building elevator control system.References[1]Liang jianqi , Duan zhengang,and He wei .CommunicationImplementation of PLC-Based Elevator Remote Monitoring System (in Chinese)[J] Journal of Beijing Technology and Business University 2003,21(2):18-21[2]Ma Hongqian ,Zhang Xin .Application of PLC in Higher Building Elevator Control System (in Chinese)[J]Journal of Liaoning Higher V ocational Technical Institute 2002,4(5): 86-88.[3]Cui Guangyuan. The Application of PLC to Elevator Control. (in Chinese)[J]Journal of Dongbei Electrical Power Technology 2003,(7): 50-52.Author BiographiesThe first author is currently working as a teacher in Taiyuan University of Technology. Her current research interests include signal processing, intelligence control etc.The second author is currently working as a teacher in Taiyuan University of science and Technology. Her current research interests include telecommunication, intelligence control etc.附录B 外文翻译PLC在智能建筑电梯控制系统中的应用摘要：本文主要讨论了智能建筑系统的一个子系统：电梯控制系统。
PLC-外文文献+翻译
Programmable logic controllerA programmable logic controller (PLC） or programmable controller is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines，amusement rides，or lighting fixtures。
PLCs are used in many industries and machines. Unlike general—purpose computers，the PLC is designed for multiple inputs and output arrangements, extended temperature ranges，immunity to electrical noise，and resistance to vibration and impact. Programs to control machine operation are typically stored in battery-backed or non-volatile memory。
A PLC is an example of a real time system since output results must be produced in response to input conditions within a bounded time, otherwise unintended operation will result.1.HistoryThe PLC was invented in response to the needs of the American automotive manufacturing industry。
关于PLC的外文及翻译
PLCs --Past, Present and FutureEveryone knows there's only one constant in the technology world, and that's change. This is especially evident in the evolution of Programmable Logic Controllers (PLC) and their varied applications. From their introduction more than 30 years ago, PLCs have become the cornerstone of hundreds of thousands of control systems in a wide range of industries.At heart, the PLC is an industrialized computer programmed with highly specialized languages, and it continues to benefit from technological advances in the computer and information technology worlds. The most prominent of which is miniaturization and communications.The Shrinking PLCWhen the PLC was first introduced, its size was a major improvement - relative to the hundreds of hard-wired relays and timers it replaced. A typical unit housing a CPU and I/O was roughly the size of a 19 television set. Through the 1980s and early 1990s, modular PLCs continued to shrink in footprint while increasing in capabilities and performance (see Diagram 1 for typical modular PLC configuration).In recent years, smaller PLCs have been introduced in the nano and micro classes that offer features previously found only in larger PLCs. This has made specifying a larger PLC just for additional features or performance, and not increased I/O count, unnecessary, as even those in the nano class are capable of Ethernet communication, motion control, on-board PID with autotune, remote connectivity and more.PLCs are also now well-equipped to replace stand-alone process controllers in many applications, due to their ability to perform functions of motion control, data acquisition, RTU (remote telemetry unit) and even some integrated HMI (human machine interface) functions. Previously, these functions often required their own purpose-built controllers and software, plus a separate PLC for the discrete control and interlocking.The Great CommunicatorPossibly the most significant change in recent years lies in the communications arena. In the 1970s Modicon introduction of Modbus communications protocol allowed PLCs to communicate over standard cabling. This translates to an ability to place PLCs in closer proximity to real world devices and communicate back to other system controls in a main panel.In the past 30 years we have seen literally hundreds of proprietary and standard protocols developed, each with their own unique advantages.Today's PLCs have to bedata compilers and information gateways. They have to interface with bar code scanners and printers, as well as temperature and analog sensors. They need multiple protocol support to be able to connect with other devices in the process. And furthermore, they need all these capabilities while remaining cost-effective and simple to program.Another primary development that has literally revolutionized the way PLCs are programmed, communicate with each other and interface with PCs for HMI, SCADA or DCS applications, came from the computing world.Use of Ethernet communications on the plant floor has doubled in the past five years. While serial communications remain popular and reliable, Ethernet is fast becoming the communications media of choice with advantages that simply can't be ignored, such as: Network speed. Ease of use when it comes to the setup and wiring. Availability of off-the-shelf networking components. Built-in communications setups.Integrated Motion ControlAnother responsibility the PLC has been tasked with is motion control. From simple open-loop to multi-axis applications, the trend has been to integrate this feature into PLC hardware and software.There are many applications that require accurate control at a fast pace, but not exact precision at blazing speeds. These are applications where the stand-alone PLC works well. Many nano and micro PLCs are available with high-speed counting capabilities and high-frequency pulse outputs built into the controller, making them a viable solution for open-loop control.The one caveat is that the controller does not know the position of the output device during the control sequence. On the other hand, its main advantage is cost. Even simple motion control had previously required an expensive option module, and at times was restricted to more sophisticated control platforms in order to meet system requirements.More sophisticated motion applications require higher-precision positioning hardware and software, and many PLCs offer high-speed option modules that interface with servo drives. Most drives today can accept traditional commands from host (PLC or PC) controls, or provide their own internal motion control. The trend here is to integrate the motion control configuration into the logic controller programming software package.Programming LanguagesA facet of the PLC that reflects both the past and the future is programming language. The IEC 61131-3 standard deals with programming languages and defines two graphical and two textual PLC programming language standards: Ladder logic (graphical). Function block diagram (graphical). Structured text (textual).Instruction list (textual).This standard also defines graphical and textual sequential function chart elements to organize programs for sequential and parallel control processing. Based on the standard, many manufacturers offer at least two of these languages as options for programming their PLCs. Ironically, approximately 96 percent of PLC users recently still use ladder diagrams to construct their PLC code. It seems that ladder logic continues to be a top choice given it's performed so well for so long.Hardware PlatformsThe modern PLC has incorporated many types of Commercial off the Shelf (COTS) technology in its CPU. This latest technology gives the PLC a faster, more powerful processor with more memory at less cost. These advances have also allowed the PLC to expand its portfolio and take on new tasks like communications, data manipulation and high-speed motion without giving up the rugged and reliable performance expected from industrial control equipment.New technology has also created a category of controllers called Programmable Automation Controllers, or PACs. PACs differ from traditional PLCs in that they typically utilize open, modular architectures for both hardware and software, using de facto standards for network interfaces, languages and protocols. They could be viewed as a PC in an industrial PLC-like package.The FutureA 2005 PLC Product Focus Study from Reed Research Group pointed out factors increasingly important to users, machine builders and those making the purchasing decisions. The top picks for features of importance were.The ability to network, and do so easily. Ethernet communications is leading the charge in this realm. Not only are new protocols surfacing, but many of the industry de facto standard serial protocols that have been used for many years are being ported to Ethernet platforms. These include Modbus (ModbusTCP), DeviceNet (Ethernet/IP) and Profibus (Profinet). Ethernet communication modules for PLCs are readily available with high-speed performance and flexible protocols. Also, many PLC CPUs are now available with Ethernet ports on board, saving I/O slot space. PLCs will continue to develop more sophisticated connectivity to report information to other PLCs, system control systems, data acquisition (SCADA) systems and enterprise resource planning (ERP) systems. Additionally, wireless communications will continue to gain popularity.The ability to network PLC I/O connections with a PC. The same trends that have benefited PLC networking have migrated to the I/O level. Many PLC manufacturers are supporting the most accepted fieldbus networks, allowing PLC I/O to be distributed over large physical distances, or located where it was previously considered nearly impossible. This has opened the door for personal computers to interface with standard PLC I/O subsystems by using interface cards, typically supplied by the PLC manufacturer or a third party developer. Now these challenging locations can be monitored with today a PC. Where industrial-grade control engines are not required, the user can take advantage of more advanced software packages and hardware flexibility at a lower cost.The ability to use universal programming software for multiple targets/platforms. In the past it was expected that an intelligent controller would be complex to program. That is no longer the case. Users are no longer just trained programmers, such as design engineers or systems integrators, but end-users who expect easier-to-use software in more familiar formats. The Windows-based look and feel that users are familiar with on their personal computers have become the most accepted graphical user interface. What began as simple relay logic emulation for programming PLCs has evolved into languages that use higher level function blocks that are much more intuitive to configure. PLC manufacturers are also beginning to integrate the programming of diverse functions that allow you to learn only one package in configuring logic, HMI, motion control and other specialized capabilities. Possibly the ultimate wish of the end-user would be for a software package that could seamlessly program many manufacturers PLCs and sub-systems. After all, Microsoft Windows operating system and applications work similarly whether installed on a Dell, HP or IBM computer, which makes it easier for the user.Overall, PLC users are satisfied with the products currently available, while keeping their eye on new trends and implementing them where the benefits are obvious. Typically, new installations take advantage of advancing technologies, helping them become more accepted in the industrial world.PLC的过去、现在与未来众所周知，科技世界里只有一个永恒真理，那就是变化。
可编程控制器外文翻译、中英文翻译、外文文献翻译
毕业设计中英文翻译院系专业班级姓名学号指导教师20**年 4 月Programmable Logic Controllers (PLC)1、MotivationProgrammable Logic Controllers (PLC), a computing device invented by Richard E. Morley in 1968, have been widely used in industry including manufacturing systems, transportation systems, chemical process facilities, and many others. At that time, the PLC replaced the hardwired logic with soft-wired logic or so-called relay ladder logic (RLL), a programming language visually resembling the hardwired logic, and reduced thereby the configuration time from 6 months down to 6 days [Moody and Morley, 1999].Although PC based control has started to come into place, PLC based control will remain the technique to which the majority of industrial applications will adhere due to its higher performance, lower price, and superior reliability in harsh environments. Moreover, according to a study on the PLC market of Frost and Sullivan [1995], an increase of the annual sales volume to 15 million PLCs per year with the hardware value of more than 8 billion US dollars has been predicted, though the prices of computing hardware is steadily dropping. The inventor of the PLC, Richard E Morley, fairly considers the PLC market as a 5-billion industry at the present time.Though PLCs are widely used in industrial practice, the programming of PLC based control systems is still very much relying on trial-and-error. Alike software engineering, PLC software design is facing the software dilemma or crisis in a similar way. Morley himself emphasized this aspect most forcefully by indicating [Moody and Morley, 1999, p. 110]:`If houses were built like software projects, a single woodpecker could destroy civilization.”Particularly, practical problems in PLC programming are to eliminate software bugs and to reduce the maintenance costs of old ladder logic programs. Though the hardware costs of PLCs are dropping continuously, reducing the scan time of the ladder logic is still an issue in industry so that low-cost PLCs can be used.In general, the productivity in generating PLC is far behind compared to other domains, for instance, VLSI design, where efficient computer aided design tools are in practice. Existent software engineering methodologies are not necessarily applicable to the PLC basedsoftware design because PLC-programming requires a simultaneous consideration of hardware and software. The software design becomes, thereby, more and more the major cost driver. In many industrial design projects, more than SO0/a of the manpower allocated for the control system design and installation is scheduled for testing and debugging PLC programs [Rockwell, 1999].In addition, current PLC based control systems are not properly designed to support the growing demand for flexibility and reconfigurability of manufacturing systems. A further problem, impelling the need for a systematic design methodology, is the increasing software complexity in large-scale projects.PLCs (programmable logic controllers) are the control hubs for a wide variety of automated systems and processes. They contain multiple inputs and outputs that use transistors and other circuitry to simulate switches and relays to control equipment. They are programmable via software interfaced via standard computer interfaces and proprietary languages and network options.Programmable logic controllers I/O channel specifications include total number of points, number of inputs and outputs, ability to expand, and maximum number of channels. Number of points is the sum of the inputs and the outputs. PLCs may be specified by any possible combination of these values. Expandable units may be stacked or linked together to increase total control capacity. Maximum number of channels refers to the maximum total number of input and output channels in an expanded system. PLC system specifications to consider include scan time, number of instructions, data memory, and program memory. Scan time is the time required by the PLC to check the states of its inputs and outputs. Instructions are standard operations (such as math functions) available to PLC software. Data memory is the capacity for data storage. Program memory is the capacity for control software.Available inputs for programmable logic controllers include DC, AC, analog, thermocouple, RTD, frequency or pulse, transistor, and interrupt inputs. Outputs for PLCs include DC, AC, relay, analog, frequency or pulse, transistor, and triac. Programming options for PLCs include front panel, hand held, and computer.Programmable logic controllers use a variety of software programming languages for control. These include IEC 61131-3, sequential function chart (SFC), function block diagram (FBD), ladder diagram (LD), structured text (ST), instruction list (IL), relay ladder logic (RLL), flow chart, C, and Basic. The IEC 61131-3 programming environment provides support for five languages specified by the global standard: Sequential Function Chart,Function Block Diagram, Ladder Diagram, Structured Text, and Instruction List. This allows for multi-vendor compatibility and multi-language programming. SFC is a graphical language that provides coordination of program sequences, supporting alternative sequence selections and parallel sequences. FBD uses a broad function library to build complex procedures in a graphical format. Standard math and logic functions may be coordinated with customizable communication and interface functions. LD is a graphic language for discrete control and interlocking logic. It is completely compatible with FBD for discrete function control. ST is a text language used for complex mathematical procedures and calculations less well suited to graphical languages. IL is a low-level language similar to assembly code. It is used in relatively simple logic instructions. Relay Ladder Logic (RLL), or ladder diagrams, is the primary programming language for programmable logic controllers (PLCs). Ladder logic programming is a graphical representation of the program designed to look like relay logic. Flow Chart is a graphical language that describes sequential operations in a controller sequence or application. It is used to build modular, reusable function libraries. C is a high level programming language suited to handle the most complex computation, sequential, and data logging tasks. It is typically developed and debugged on a PC. BASIC is a high level language used to handle mathematical, sequential, data capturing and interface functions.Programmable logic controllers can also be specified with a number of computer interface options, network specifications and features. PLC power options, mounting options and environmental operating conditions are all also important to consider.2、ResumeA PLC (programmable Logic Controller) is a device that was invented to replace the necessary sequential relay circuits for control.The PLC works by looking at its input and depending upon their state, turning on/off its outputs. The user enters a program, usually via software or programmer, which gives the desired results.PLC is used in many "real world" applications. If there is industry present, chance are good that there is a PLC present. If you are involved in machining, packing, material handling, automated assembly or countless other industries, you are probably already using them. If you are not, you are wasting money and time. Almost any application that needs some type of electrical control has a need for a PLC.For example, let's assume that when a switch turns on we want to turn a solenoid on for 5second and then turn it off regardless of how long the switch is on for. We can do this with a simple external timer. But what if the process included 10 switches and solenoids? We should need 10 external times. What if the process also needed to count how many times the switch individually turned on? We need a lot of external counters.As you can see the bigger the process the more of a need we have for a PLC. We can simply program the PLC to count its input and turn the solenoids on for the specified time.We will take a look at what is considered to be the "top 20" PLC instructions. It can be safely estimated that with a firm understanding of these instructions one can solve more than 80% of the applications in existence.Of course we will learn more than just these instruction to help you solve almost ALL potential PLC applications.The PLC mainly consists of a CPU, memory areas, and appropriate circuits to receive input/output data. We can actually consider the PLC to be a box full of hundreds or thousands of separate relay, counters, times and data storage locations,Do these counters,timers, etc. really exist? No,they don't "physically" exist but rather they simulated and be considered software counters, timers, etc. . These internal relays are simulated through bit locations in registers.What does each part do? Let me tell you.Input RelaysThese are connected to the outside world.They physically exsit and receive signals from switches,sensors,ect..Typically they are not relays but rather they are transistors.Internal Utility RelaysThese do not receive signals from the outside world nor do they physically exist.they are simulated relays and are what enables a PLC to eliminate external relays.There are also some special relays that are dedicated to performing only one task.Some are always on while some are always off.Some are on only once during power-on and are typically used for initializing data that was stored.CountersThese again do not physically exist. They are simulated counters and they can be programmed to count pulses.Typically these counters can count up,down or both up anddown.Since they are simulated,they are limited in their counting speed.Some manufacturers also include high-speed counters that are hardware based.We think of these as physically existing.Most times these counters can count up,down or up and down.TimersThese also do not physically exist.They come in many varieties and increments.The most common type is an on-delay type.Others include off-delays and both retentive and non-retentive types.Increments vary from 1ms through 1s.Output RelaysThere are connected to the outside world.They physically exist and send on/off signals to solenoids,lights,etc..They can be transistors,relays,or triacs depending upon the model chosen Data StorageTypically there are registers assigned to simply store data.They are usually used as temporary storage for math or data manipulation.They can also typically be used to store data when power is removed form the PLC.Upon power-up they will still have the same contents as before power was moved.Very convenient and necessary!A PLC works by continually scanning a program.We can think of this scan cycle as consisting of 3 important steps.There are typically more than 3 but we can focus on the important parts and not worry about the others,Typically the others are checking the system and updating the current internal counter and timer values,Step 1 is to check input status,First the PLC takes a look at each input to determine if it is on off.In other words,is the sensor connected to the first input on?How about the third...It records this data into its memory to be used during the next step.Step 2 is to execute program.Next the PLC executes your program one instruction at a time.Maybe your program said that if the first input was on then it should turn on the first output.Since it already knows which inputs are on/off from the previous step,it will be able to decide whether the first output should be turned on based on the state of the first input.It will store the execution results for use later during the next step.Step 3 is to update output status.Finally the PLC updates the status the outputs.It updates the outputs based on which inputs were on during the first step and the results executing your program during the second step.Based on the example in step 2 it would now turn on the firstoutput because the first input was on and your program said to turn on the first output when this condition is true.After the third step the PLC goes back to step one repeats the steps continuously.One scan time is defined as the time it takes to execute the 3 steps continuously.One scan time is defined as the time it takes to execute the 3 steps listed above.Thus a practical system is controlled to perform specified operations as desired.3、PLC StatusThe lack of keyboard, and other input-output devices is very noticeable on a PLC. On the front of the PLC there are normally limited status lights. Common lights indicate;power on - this will be on whenever the PLC has powerprogram running - this will often indicate if a program is running, or if no program is runningfault - this will indicate when the PLC has experienced a major hardware or software problemThese lights are normally used for debugging. Limited buttons will also be provided for PLC hardware. The most common will be a run/program switch that will be switched to program when maintenance is being conducted, and back to run when in production. This switch normally requires a key to keep unauthorized personnel from altering the PLC program or stopping execution. A PLC will almost never have an on-off switch or reset button on the front. This needs to be designed into the remainder of the system.The status of the PLC can be detected by ladder logic also. It is common for programs to check to see if they are being executed for the first time, as shown in Figure 1. The ’first scan’ input will be true on the very first time the ladder logic is scanned, but false on every other scan. In this case the address for ’first scan’ in a PLC-5 is ’S2:1/14’. With the logic in the example the first scan will seal on ’light’, until ’clear’ is turned on. So the light will turn on after the PLC has been turned on, but it will turn off and stay off after ’clear’ is turned on. The ’first scan’ bit is also referred to at the ’first pass’ bit.Figure 1 An program that checks for the first scan of the PLC4、Memory TypesThere are a few basic types of computer memory that are in use today.RAM (Random Access Memory) - this memory is fast, but it will lose its contents when power is lost, this is known as volatile memory. Every PLC uses this memory for the central CPU when running the PLC.ROM (Read Only Memory) - this memory is permanent and cannot be erased. It is often used for storing the operating system for the PLC.EPROM (Erasable Programmable Read Only Memory) - this is memory that can be programmed to behave like ROM, but it can be erased with ultraviolet light and reprogrammed.EEPROM (Electronically Erasable Programmable Read Only Memory) – This memory can store programs like ROM. It can be programmed and erased using a voltage, so it is becoming more popular than EPROMs.All PLCs use RAM for the CPU and ROM to store the basic operating system for the PLC. When the power is on the contents of the RAM will be kept, but the issue is what happens when power to the memory is lost. Originally PLC vendors used RAM with a battery so that the memory contents would not be lost if the power was lost. This method is still in use, but is losing favor. EPROMs have also been a popular choice for programming PLCs. The EPROM is programmed out of the PLC, and then placed in the PLC. When the PLC is turned on the ladder logic program on the EPROM is loaded into the PLC and run. This method can be very reliable, but the erasing and programming technique can be time consuming. EEPROM memories are a permanent part of the PLC, and programs can be stored in them like EPROM. Memory costs continue to drop, and newer types (such as flash memory) are becoming available, and these changes will continue to impact PLCs.5、Objective and Significance of the ThesisThe objective of this thesis is to develop a systematic software design methodology for PLC operated automation systems. The design methodology involves high-level description based on state transition models that treat automation control systems as discrete event systems, a stepwise design process, and set of design rules providing guidance and measurements to achieve a successful design. The tangible outcome of this research is to find a way to reduce the uncertainty in managing the control software development process, that is, reducing programming and debugging time and their variation, increasing flexibility of theautomation systems, and enabling software reusability through modularity. The goal is to overcome shortcomings of current programming strategies that are based on the experience of the individual software developer.A systematic approach to designing PLC software can overcome deficiencies in the traditional way of programming manufacturing control systems, and can have wide ramifications in several industrial applications. Automation control systems are modeled by formal languages or, equivalently, by state machines. Formal representations provide a high-level description of the behavior of the system to be controlled. State machines can be analytically evaluated as to whether or not they meet the desired goals. Secondly, a state machine description provides a structured representation to convey the logical requirements and constraints such as detailed safety rules. Thirdly, well-defined control systems design outcomes are conducive to automatic code generation- An ability to produce control software executable on commercial distinct logic controllers can reduce programming lead-time and labor cost. In particular, the thesis is relevant with respect to the following aspect Customer-Driven ManufacturingIn modern manufacturing, systems are characterized by product and process innovation, become customer-driven and thus have to respond quickly to changing system requirements.A major challenge is therefore to provide enabling technologies that can economically reconfigure automation control systems in response to changing needs and new opportunities. Design and operational knowledge can be reused in real-time, therefore, giving a significant competitive edge in industrial practice.Higher Degree of Design Automation and Software QualityStudies have shown that programming methodologies in automation systems have not been able to match rapid increase in use of computing resources. For instance, the programming of PLCs still relies on a conventional programming style with ladder logic diagrams. As a result, the delays and resources in programming are a major stumbling stone for the progress of manufacturing industry. Testing and debugging may consume over 50% of the manpower allocated for the PLC program design. Standards [IEC 60848, 1999; IEC-61131-3, 1993; IEC 61499, 1998; ISO 15745-1, 1999] have been formed to fix and disseminate state-of-the-art design methods, but they normally cannot participate in advancingthe knowledge of efficient program and system design.A systematic approach will increase the level of design automation through reusing existing software components, and will provide methods to make large-scale system design manageable. Likewise, it will improve software quality and reliability and will be relevant to systems high security standards, especially those having hazardous impact on the environment such as airport control, and public railroads.System ComplexityThe software industry is regarded as a performance destructor and complexity generator. Steadily shrinking hardware prices spoils the need for software performance in terms of code optimization and efficiency. The result is that massive and less efficient software code on one hand outpaces the gains in hardware performance on the other hand. Secondly, software proliferates into complexity of unmanageable dimensions; software redesign and maintenance-essential in modern automation systems-becomes nearly impossible. Particularly, PLC programs have evolved from a couple lines of code 25 years ago to thousands of lines of code with a similar number of 1/O points. Increased safety, for instance new policies on fire protection, and the flexibility of modern automation systems add complexity to the program design process. Consequently, the life-cycle cost of software is a permanently growing fraction of the total cost. 80-90% of these costs are going into software maintenance, debugging, adaptation and expansion to meet changing needs [Simmons et al., 1998].Design Theory DevelopmentToday, the primary focus of most design research is based on mechanical or electrical products. One of the by-products of this proposed research is to enhance our fundamental understanding of design theory and methodology by extending it to the field of engineering systems design. A system design theory for large-scale and complex system is not yet fully developed. Particularly, the question of how to simplify a complicated or complex design task has not been tackled in a scientific way. Furthermore, building a bridge between design theory and the latest epistemological outcomes of formal representations in computer sciences and operations research, such as discrete event system modeling, can advance future development in engineering design.Application in Logical Hardware DesignFrom a logical perspective, PLC software design is similar to the hardware design of integrated circuits. Modern VLSI designs are extremely complex with several million parts and a product development time of 3 years [Whitney, 1996]. The design process is normally separated into a component design and a system design stage. At component design stage, single functions are designed and verified. At system design stage, components are aggregated and the whole system behavior and functionality is tested through simulation. In general, a complete verification is impossible. Hence, a systematic approach as exemplified for the PLC program design may impact the logical hardware design.可编程控制器1、前言可编程序的逻辑控制器（PLC），是由Richard E.Morley 于1968年发明的，如今已经被广泛的应用于生产、运输、化学等工业中。
关于PLC的中英文献翻译工业控制系统
INDUSTRIAL AND COLLABORATIVECONTROL SYSTEMS 之袁州冬雪创作- A COMPLEMENTARY SYMBIOSIS –-Looking at today’s control system one can find a wide variety of implementations. From pure industrial to collaborative control system (CCS) tool kits to home grown systems and any variation in-between. Decisions on the type of implementation should be driven by technical arguments Reality shows that financial and sociological reasons form the complete picture.Any decision has it’s advantages and it’s drawbacks. Reliability, good documentation and support are arguments for industrial controls.Financial arguments drive decisions towards collaborative tools. Keeping the hands on the source code and being able to solve problems on your own and faster than industry are the argument for home grown solutions or open source solutions. The experience of many years of operations shows that which solution is the primary one does not matter, there are always areas where at least part of the other implementations exist. As a result heterogeneous systems have to be maintained. The support for different protocols is essential. This paper describes our experience with industrial control systems, PLC controlled turn key systems, the CCS tool kit EPICS and the operability between all of them.-INTRODUCTIONProcess controls in general started at DESY in the early 80th with the installation of the cryogenic control system for the accelerator HERA (Hadron-Elektron-Ring-Anlage). A new technology was necessary because the existing hardware was not capable to handle standard process controls signals like 4 to 20mA input and output signals and the software was notdesigned to run PID control loops at a stable repetition rate of 0.1 seconds. In addition sequence programs were necessary to implement startup and shutdown procedures for the complex cryogenic processes like cold boxes and compete compressor streets.Soon it was necessary to add interfaces to field buses and to add computing power to cryogenic controls. Since the installed D/3 system[1] only provided an documented serial connection on a multibus board, the decision was made to implement a DMA connection to VME and to emulate the multibus board’s functionality. The necessary computing power for temperature conversions came from a Motorola MVME 167 CPU and the field bus adapter to the in house SEDAC field bus was running on an additional MVME 162.The operating system was VxWorks and the application was the EPICS toolkit.Since this implementation was successful it was also implemented for the utility controls which were looking for a generic solution to supervise their distributed PLC’s.A SELECTION OF PROCESS CONTROL SYSTEMS AT DESYDCS (D/3)As a result of a market survey the D/3 system from GSE was selected for the HERA cryogenic plant. The decision was fortunate because of the DCS character of the D/3. The possibility to expand the system on the display- and on the I/O side helped to solve the increasing control demands for HERA. The limiting factor for the size of the system is not the total number of I/O but the traffic on the communication network.This traffic is determined by the total amount of archived data not by the data configured in the alarm system. The technical background of this limitation is the fact that archived data are polled from the display servers whereas the alarms are pushed to configured destinationslike alarm-files, (printer) queues or displays. SCADA Systems with DCS Features (Cube)The fact that the D/3 system mentioned above had some hard coded limitations with respect to the Y2K problem was forcing us to look for an upgrade or a WordStrment of the existing system.As a result of a call for tender the company Orsi with their product Cube came into play [2].The project included a complete WordStrment of the installed functionality. This included the D/3 as well as the integration of the DESY field bus SEDAC and the temperature conversion in VME.The project started promising. But soon technical and organizational problems were pushing the schedule to it’s limits wh ich were determined by the HERA shutdown scheduled at that time. The final acceptance test at the vendors site showed dramatic performance problems. Two factors could be identified as thecause of these problems. The first one was related to the under estimated CPU load of the 6th grade polynomial temperature conversion running at 1 Hz. The second one was the additional CPU load caused by the complex functionality of the existing D/3 system. Here it was underestimated that each digital and analog input and output channel had it’s own alarm limits in the D/3 system. In a SCADA like system as Cube the base functionality of a channel is to read the value and make it available to the system. Any additional functionality must be added. Last not least the load on the network for polling all the alarm limits –typically for a SCADA system –was also driving the network to it’s limits.Finally the contract with Orsi was cancelled and an upgrade of the D/3 system was the only possible solution. It was finally carried out in march 2003.In any case it should be mentioned that the Cube approach had the advantage of a homogeneousconfiguration environment (for the Cube front end controllers) –compared with heterogeneous environments for ‘pure’ SCADA systems.SCADA (PVSS-II)The H1 experiment at the HERA accelerator decided to use PVSS-II for an upgrade of their slow control systems[3]. The existing systems were developed by several members of the H1 collaboration and were difficult to maintain.The decision to use PVSS as a WordStrment was driven by the results of an extensive survey carried out at CERN by the Joint Controls Project [4]. PVSS is a ‘pure’ Supervisory And Data Acquisition System (SCADA). It provides a set of drivers for several field buses and generic socket libraries to implement communication over TCP/IP. The core element is the so called event manager. It collects the data (mostly by polling) from the I/O devices and provides an event service to the attachedmanagement services like: control manager, database manager, user interface, API manager and the built in HTTP server. The PVSS scripting library allows to implement complex sequences as well as complex graphics. Compared with other SCADA systems PVSS comes with one basic feature: it provides a true object oriented API to the device’s data.One major disadvantage of SCADA systems is the fact that two databases, the one for the PLC and the one for the SCADA system must be maintained.Integrated environments try to overcome this restriction.EPICSEPICS has emerged at DESY from a problem solver to a fully integrated control system. Starting from the data collector and number cruncher for the cryogenic control system, EPICS made it’s way to become the core application for the DESY utility group. In addition it is used whereverdata is available through VME boards or by means of Industry Pack (IP) modules. For those cryogenic systems which are not controlled by the D/3 system EPICS is used with it’s complete functionality. In total about 50 Input Output Controller (IOC) are operational processing about 25 thousand records.1 EPICS as a SCADA SystemThe utility group ( water, electrical power, compressed air, heating and air conditioning) is using a variety of PLC’s spread out over the whole DESY site. EPICS is used to collect the data from these PLC’s over Profibus (FMS and DP) and over Ethernet (Siemens H1 and TCP). The IOC’s provide the interfaces to the buses and collect the data. The built in alarm checking of the EPICS records is used to store and forward alarm states to the alarm handler (alh) of the EPICS toolkit. In addition tools like the channel archiver and the graphic display (dm2k) are used.The default name resolution (by UDP broadcast) and the directory server (name server) are used to connectclient and server applications over TCP. All of these are basically SCADA functions.The textual representation of all configuration files ( for the IOC, the graphic tool, the alarm handler and the archiver) provides a flexible configuration scheme. At DESY the utility group has developed a set of tools to create IOC databases and alarm configuration files from Oracle. This way the controls group provides the service to maintain the EPICS tools and the IOC’s while the users can concentrate on the equipment being controlled.2 EPICS as a DCS SystemBesides the basic components of a SCADA system EPICS also provides a full flavoured Input Output Controller (IOC). The IOC provides all of the function a DCS system requires, such as: astandard set of properties implemented in each record, built in alarm checking processed during the execution of each record; control records like PID etc.; configuration tools for the processing engine. The flexible naming scheme and the default display and alarm properties for each record ease the connection between the operator tools and the IOC’s. The flexible data acquisition supports the poll mode as well as the publish subscribe mode. The latter reduces the traffic drastically.PLC’sPLC’s provide nowadays the same rich functionality as it was known from stand alone control systems in the past. Besides the basic features like the periodic execution of a defined set of functions they also allow extensive communication over Ethernet including embedded http servers and different sets ofcommunication programs. Besides the communication processors, display processors can be linked to PLC’s to provide local displays which can be comprised as touch panels for operator intervention and value settings.These kind of PLC’s are att ractive for turn key systems which are commissioned at the vendors site and later integrated into the customers control system.Intelligent I/ONew developments in I/O devices allow to ‘cluster’ I/O in even smaller groups and connect theses clustered I/O channels directly to the control system. PLC’s are not any more necessary for distributed I/O. Simple communication processors for any kind of field buses or for Ethernet allow an easy integration into the existing controls infrastructure.Little local engines can run IEC 61131 programs.The differences between PLC’s and intelligent I/O subsystems fade away.FUNCTIONALITYThe ever lasting question why control systems for accelerators and other highly specialized equipment are often home grown or at least developed in a collaboration but only in rare cases commercial shall not be answered here. We try to summarize here basic functionalities of different controls approaches.Front-end ControllerOne of the core elements of a control system is the front-end controller. PLC’s can be used to implement most of the functions to control the equipment. The disadvantage is the complicated access to the controls properties. For instance all of the properties of a control loop like the P, I and D parameter, but also the alarm limits and other additional properties must beaddressed individually in order to identify them in the communication protocol and last not least in the display-, alarm- and archive programs. In addition any kind of modifications of theseembedded properties is difficult to track because two or more systems are involved. This might be one strong argument why control loops are mainly implemented on the IOC level rather than PLC’s.1 I/O and Control LoopsComplex control algorithms and control loops are the domain of DCS alike control systems. The support for sets of predefined display and controls properties is essential. If not already available (like in DCS systems) such sets of generic properties are typically specified throughout a complete control system (see namespaces).2 Sequence/ State programsSequence programs can run on any processor in a control system. The runtime environment dependson the relevance of the code for the control system. Programs fulfilling watchdog functions have to run on the front-end processor directly.Sequence programs for complicated startup and shutdown procedures could be run on a workstation as well. The basic functionality ofa state machine can be even implemented in IEC61131. Code generators can produce ‘C’ code which can be compiled for the runtime environment.3 Supported HardwareThe support for field buses and Ethernet based I/O is a basic functionality for SCADA type systems it is commercially available from any SCADA system on the market. The integration of specific hardware with specific drivers and data conversion is the hard part in a commercialenvironment. Open API’s or scripting support sometimes help to integrate custom hardware. If these tools are not provided for the controlsystem it is difficult – if not impossible - to integrate custom hardware.New industrial standards like OPC allow the communication with OPC aware devices and the communication between control systems. One boundary condition for this kind of functionality is the underlying operating system.In the case of OPC it is bound to DCOM which isa Microsoft standard. UNIX based control systemshave a hard time to get connected. Only control systems supporting multiple platforms can play a major role in a heterogeneous environments.As a result the limited support for custom- or specialized hardware may give reason for the development of a new control system.Display and OperationBesides the front-end system the operator interfaces play a major role for the acceptance of a control system. SCADA tools come with ahomogeneous look and feel throughout their set of tools. Toolkits implemented in a collaboration might vary because the individual tools were developed by different teams.1 GraphicSynoptic displays are the advertising sign for any control system. Commercial synoptic displays come with a rich functionality and lots of special features. Starting to make use of all these features one will find out that all individual properties of the graphic objects must be specified individually. Since SCADA systems must be generic they cannot foresee that an input channel does not only consist of a value but also consists of properties like display ranges and alarm values. Defining all of these properties again and again can be a pretty boring job. Some systems allow to generate prototypes of graphic objects. These prototype or template graphics are complex and need a specialist to generate them.DCS or custom synoptic display programs can make use of the common set of properties each I/O point provides. This predefined naming scheme will fill in all standard property values and thus only require to enter the record –or device name into the configuration tool. A clear advantage for control systems with a notion of I/O objects rather than I/O points.2 AlarmingAlarms are good candidates to distinguishbetween different control system architectures. Those systems which have I/O object implemented also provide alarm checking on the front-end computer. Those systems which only know about I/O points have to add alarm checking into the I/O processing. While the I/O object approach allows to implement alarm checking in the native programming language of the front-end system, I/O point oriented systems typically have to implement this functionality in their native scripting language. This is typically less efficient and error prone because all properties must be individually configured. This leads to a flood of properties. Not only the error states for each I/O point wind up to be individual I/O points but also the alarm limits and the alarm severity of each limit must be defined as I/O points if it is desired to be able to change their values during runtime.Besides this impact on the configuration side the processing and forwarding of alarms makes the difference between SCADA and DCS systems.Since SCADA systems inherently do not ‘know’ about alarms, each alarm state must be polled either directly from the client application or in advanced cases from an event manager which will forward alarm states to the clients. In any case a lot of overhead for ‘just’ checking alarm limits. DCS system again have the advantage that clients can either register themselves for alarm states und thus get the information forwarded or are configured to send alarmchanges to certain destinations spread around the control system. The latter case is only possible for systems which in total are configured with all the nodes taking part in the controls network.3 Trending and ArchivingTrending has become an important business incontrol systems architectures. Trends are necessary to trace error conditions or for post mortem and performance analysis of the controlled plant. Besides some customimplementations which are capable to store the data of complete control objects, most of the trending tools archive scalar data. Additional features like conditional trending or correlation plots make up the difference between individual implementations.4 Programming InterfacesWith respect to open programming interfaces PLC’s and DCS systems have a common strategy.They are running reliably because there’s noway to integrate custom code which could interfere with the internal processing. As a consequence the customer has to order‘specials’ - which are extremely expensive –or forget about it and use the system as a black box.Since SCADA systems by definition must be able to communicate with a variety of I/O subsystems they already have some built in API’s whichallow to integrate custom functionality.Specially collaborative systems need a certain openness to fulfill all the requirements fromvarious development groups. Programming interfaces on all levels like font-end I/O, front-end processing, networking etc. aremandatory. A clear advantage for this type of system.5 RedundancyIf redundancy means the seamless switch which takes over all the states and all the values of the I/O and all states of all programs currently running, it is a domain of only a few DCS systems. Custom or CCS implementation do not provide this kind of functionality. Maybe because of the immense effort and the fact that it is only required in rare cases.Besides processor redundancy, redundant networks or I/O subsystems are available for certain commercial DCS systems. Again – a domain which is not covered by SCADA or CCS implementations.Advanced safety requirements may be covered byredundant PLC subsystems. These are for instance installed in (nuclear) power plants.Requirements for Personal Protection Systems(PPS) can sometimes only be fulfilled by redundant PLC’s. In process controls redundantPLC’s are only used in rare cases.6 NamespaceThe flat namespace of SCADA systems has already been described in the alarm section. Some SCADA systems (like PVSS-II) provide the notion ofcontrol objects or structured data which is a rare case. In all other cases so called field objects must be specified. These are objects which consist of a list of properties (implemented as I/O points) and a set of methods ( implemented asmacros or function calls). Oneof these approaches is the UniNified Industrial COntrol System (UNICOS) at CERN [5].DCS systems and most of the custom/collaborative systems are record –or device oriented. The difference being that typically one record is connected to a single I/O pointand provides this way all sub features of a record implementation like individual engineering units, display- and alarm limits.The device oriented approach allows to connect several I/O points. The major difference being the fact that an object oriented device implementation provides methods and states for a device while (EPICS) records only serve a certain set of built in functions.Naming hierarchies are not specific to a type of implementation. They are available for some systems of any kind. For sure hierarchical naming schemes are desirable.IMPLEMENTATION STRATEGIESAfter having shown all the possible controls approaches it is time to have a look at the implementation of control systems.Starting from the I/O level one has to decide whether commercial solution are required, feasible or wanted. Special I/O does not alwaysrequire custom solution for the font-end controller. Signals can be converted into standard signals but this does not apply for all kinds of signals. Resolution, repetition rates and signal levels might require custom developments which must be integrated into the overall control architecture. Even if the signals can not be connected to standard I/O interfaces it might be possible to develop I/O controllers which implement a field bus interface which allow the integration with commercial control systems. Once this level of integration is not possible custom front-end controllers like VME crates come into play.Besides the decision whether special I/O requires dedicated custom solutions one has to decide who will do which part of the work? Does for instance the necessity of VME crates prohibit the delivery of a ‘turn key’ systembuilt by industry? Or does a PLC based front-end system require a commercial SCADA system for high level controls?Turn Key SystemsIt is a clear trend in industry to deliver turn key systems. It allows a modular design of the whole system. Individual components can be subcontracted to several companies and tested locally. Once delivered to the construction site the primary acceptance tests have already been passed and the second phase, to integrate the subsystem into the global control system begins.While the detailed specification of control loops etc. is now part of the subsystems contract, the customer has to specify clearly how much information of the subsystem must be made available, what the data structures will look like and which connection (field bus/ Ethernet) will be used.Most turn key systems are delivered with PLC’s.The construction of the Swiss Light Source (SLS)has shown that also a VME based I/O system running a CCS –in this case EPICS –can be successfully commissioned [6].PLC Based SystemsPLC based systems are a consequence of the turn key ansatz. The next obvious approach might be to look besides commercial PLC’s also for commercial SCADA systems. The advantage is clearly the same like for the PLC: stable software, no programming –only configuration, support and good documentation. At DESY we have successfully established a relation between the controls group which provides a CCS service based on EPICS and the utility group which uses the EPICS configuration tools to set up their control environment. The big advantage though being that the EPICS code can be adjusted to the special requirements from both sides.Industrial SolutionsThe difference between CCS solutions and commercial solutions is fading away as soon as industry starts to deliver and support collaborative control systems. At KEK a company was contracted to supply programmers for the KEK-B upgrade. These programmers were trained in writing drivers and application code for EPICS.As a result the KEK-B control system is a mixture of software developed partly by industry and partly in house. This is another example for an industrial involvement for a CCS implementation.COSTThe question: “Was is the total cost of ownership (TCO) of a PC?” has kept people busy since PC’s exist. The answers vary to all extremes. The question what is the TCO of a control system might give similar results.If you go commercial you have to pay for the initial licenses the implementation which istypically carried out by the supplier or by a subcontractor, and you pay for the on going software support which might or might not include the update license fee.If you go for a collaborative approach, you might contract a company or implement everything on your own. A question of ‘time and money’ as industry says. You will have more freedom and flexibility for your implementations but also a steeper learning curve. You can rely on the collaboration to provide new features and versions or you can contribute yourself. A major difference calculating the long term costs for a control system.At DESY one can roughly estimate that the (controls application)-support for a commercial approach –here D/3 - and the -support for a collaborative approach – here EPICS - is nearly the same. The software support and upgradelicense fee is equivalent to one and a half FTE’s –which is about the manpower necessary to support new hardware and to upgrade EPICS.CONCLUSIONSDepending on the size and the requirements for a controls project the combination of commercial solutions and solutions based on a collaborative approach is possible in any rate between 0 and 100 percent. This applies for all levels from implementation to long term support. Special requirements on safety issues or a lack of manpower might turn the scale commercial. The necessity to interface special hardware, special timing requirements, the ‘having the code in my hands’ argument or the initial costs for commercial solutions will turn the scale collaborative. As long as collaborative approaches like EPICS stay up to date and run as stable and robust as commercial solutions, both will keep their position in the controls world in a complementary symbiosis.外文资料翻译外文翻译译文工业节制系统和协同节制系统当今的节制系统被广泛运用于许多范畴.从单纯的工业节制系统到协同节制系统（CCS），节制系统不断变更，不竭升级，现在则趋向于家庭节制系统，而它则是这二者的变种.被应用的节制系统的种类取决于技术要求.而且，实践标明，经济和社会因素也对此很重要.任何决定都有它的优缺点.工业节制要求靠得住性，完整的文献记载和技术支持.经济因素使决定趋向于协同工具.可以亲自接触源码并可以更疾速地处理问题是家庭节制系统的要求.多年的操纵经历标明哪一个处理方法是最主要的不重要，重要的是哪一个可行.由于异类系统的存在，针对分歧协议的支持也是至关重要的.本文先容工业节制系统，PlC controlled turn key系统，和CCS工具，以及它们之间的操纵.引言：80年月早期，随着为HERA(Hadron-Elektron-Ring-Anlage)加速器装置低温节制系统，德国电子同步加速器研究所普遍开端研究过程节制.这项新技术是必须的，因为但是现有的硬件没有才能来处理尺度过程节制信号，如4至20毫安的电流输入和输出信号.而且软件无法在秒的稳定重复率下运行PID节制回路.此外，在实现对复杂的低温冷藏系统的开闭过程中，频率项目显得尤为重要.有需要增加接口处理总线问题并增加运算才能，以便于低温节制.因为已装置的D / 3系统[1] 只提供了与多总线板串行毗连，以实现DMA与VME的毗连并用其摹拟多总线板的功能.温度转换器的计算功能来自一个摩托罗拉MVME 167 CPU和总线适配器，以及一个MVME 162 CPU.其操纵系统是VxWorks，而应用程序是EPICS.由于对它的应用相当成功，其还被运用于正在寻找一个通用的处理方案以监督他们的分布式PLC的公共事业管理.德国电子同步加速器研究所对过程管理系统的筛选集散节制系统（D/ 3）：市场调查标明：来自GSE的D / 3系统被HERA低温冷藏工厂选中.因为集散节制系统（D/ 3）的特性，所以这决定很不错.在展示端和I / O端扩大此系统的可以将有助于处理日益增加的HERA试验节制的要求.制约系统的大小的因素不是I / O的总数，通信网络的疏通与否.而通信网络的疏通与否取决于不存档的数据总量，不取决于报警系统中配置的数据.拥有DCS特点（Cube）的SCADA系统：相对于Y2K问题促使我们寻找一个升级版或者代替版来代替现有的系统而言，以上提到的 D / 3系统有一些硬编码的限制.由于急需给Orsi公司提供他们的产品，Cube开端起作用了[2].该项目包含装置功能的完全更换.这包含 D /3，以及德国电子同步加速器研究所的集成总线SEDAC和VME的温度转换器.该项目很有前景.但是因为HERA试验原定时间是有限制的，所以技术问题和组织问题也迫使计划提前.在供应商网站上的最后验收测试又出现了戏剧性的性能问题.有两个因素引起了这些问题.第一个跟低估在1赫兹运行的6级温度转换器的CPU负荷有关.第二个由现有D / 3系统复杂的功能造成的额外负荷引起的.每一个数字和摹拟输入和输出通道在 D / 3系统里的自身报警限值也被低估了.所有的附加功能都必须添加出来.最后，所有网络负载的报警限值，尤其是SCADA系统，也促使网络生成了限制.最后，与Orsi公司的合同被取消了.升级的D / 3系统是唯一可以的处理法子.在2003年3月，此系统最后被付诸实践.现在，相比“纯粹”SCADA系统的异质环境，Cube有同质配置环境的优势.SCADA（PVSS -Ⅱ）：在HERA加速器上的H1实验中，实验人员为升级他们的低速节制系统，决定使用PVSS -Ⅱ.现有的系统是由H1合作组的几名成员开辟的，而现在却难以维持了.在CERN由结合节制项目[4]停止的广泛调查促使他们做出使用PVSS作为代替品的决定.PVSS是一个“纯粹”的监控和数据收集系统（SCADA系统）.其核心元素叫做事件管理器.它收集的数据主要是由I/ O设备提供.它还提供附加的管理服务，如：节制司理，数据库管理，用户界面，API司理以及在建的HTTP服务器.该PVSS剧本库允许执行复杂的序列以及复杂的图形.相比其他SCADA系统PVSS带有一个基本特点：它提供了API给设备的数据.SCADA系统的一个主要缺点是其中的两个数据库，一个为PLC’s服务，另外一个为SCADA系统服务，这两个数据库必须维持.集成环境将尽力降服这个限制.EPICS：在德国电子同步加速器研究所，EPICS从问题处理系统演化成了全集成节制系统.从成为低温节制系统的数据收集器和数量节制器，EPICS成为了德国电子同步加速器研究所公用事业集团使用的核心系统.此外，通过Industry Pack （IP）模块的手段，它还能运用于通过VME板卡的任何数据.EPICS通过其完整的功能，运用于没有由 D / 3系统节制的低温冷藏系统.所有大约50个输入输出节制器运作大约25000业务处理记录.作为一个SCADA系统的EPICS：该公共事业组（水，电，压缩空气，加热和调温）使用各种散布在整个德国电子同步加速器研究所网站上的PLC.IOC 向客户提供接口并收集数据.此外，如通道归档和图形显示。
关于PLC的中英文献翻译工业控制系统
INDUSTRIAL AND COLLABORATIVECONTROL SYSTEMS 之迟辟智美创作- A COMPLEMENTARY SYMBIOSIS –-Looking at today’s control system one can find a wide variety of implementations. From pure industrial to collaborative control system (CCS) tool kits to home grown systems and any variation in-between. Decisions on the type of implementation should be driven by technical arguments Reality shows that financial and sociological reasons form the complete picture. Any decision has it’s advantages and it’s drawbacks. Reliability, good documentation and support are arguments for industrial controls. Financial arguments drive decisions towards collaborative tools. Keeping the hands on the source code and being able to solve problems on your own and faster than industry are the argument for home grown solutions or open source solutions. The experience of many years of operations shows that which solution is the primary one does not matter, there are always areas where at least part of the other implementations exist. As a result heterogeneous systems have to be maintained. The support for different protocols is essential. This paper describes our experience with industrial control systems, PLC controlled turn key systems, the CCS tool kit EPICS and the operability between all of them.-INTRODUCTIONProcess controls in general started at DESY in the early 80th with the installation of the cryogenic control system for the accelerator HERA (Hadron-Elektron-Ring-Anlage). A new technology was necessary because the existing hardware was not capable to handle standard process controls signals like 4 to 20mA input and output signals and the software was not designed to run PID control loops at a stable repetition rate of 0.1 seconds. In addition sequence programs were necessary to implement startup and shutdown procedures for the complex cryogenic processes like cold boxes and compete compressor streets.Soon it was necessary to add interfaces to field buses and to add computing power to cryogenic controls. Since the installed D/3 system[1] only provided an documented serialconnection on a multibus board, the decision was made to implement a DMA connection to VME and to emulate the multibus board’s functionality. The necessary computing power for temperature conversions came from a Motorola MVME 167 CPU and the field bus adapter to the in house SEDAC field bus was running on an additional MVME 162.The operating system was VxWorks and the application was the EPICS toolkit.Since this implementation was successful it was also implemented for the utility controls which were looking for a generic solution to supervise their distributed PLC’s.A SELECTION OF PROCESS CONTROL SYSTEMS AT DESYDCS (D/3)As a result of a market survey the D/3 system from GSE was selected for the HERA cryogenic plant. The decision was fortunate because of the DCS character of the D/3. The possibility to expand the system on the display- and on the I/O side helped to solve the increasing control demands for HERA. The limiting factor for the size of the system is not the total number of I/O but the traffic on the communication network. This traffic is determined by the total amount of archived data not by the data configured in the alarm system.The technical background of this limitation is the fact that archived data are polled from the display servers whereas the alarms are pushed to configured destinations like alarm-files, (printer) queues or displays.SCADA Systems with DCS Features (Cube)The fact that the D/3 system mentioned above had some hard coded limitations with respect to the Y2K problem was forcing us to look for an upgrade or a WordStrment of the existing system. As a result of a call for tender the company Orsi with their product Cube came into play [2]. The project included a complete WordStrment of the installed functionality. This included the D/3 as well as the integration of the DESY field bus SEDAC and the temperature conversion in VME. The project started promising. But soon technical and organizational problemswere pushing the schedule to it’s limits wh ich were determined by the HERA shutdown scheduled at that time.The final acceptance test at the vendors site showed dramatic performance problems. Two factors could be identified as the cause of these problems. The first one was related to the under estimated CPU load of the 6th grade polynomial temperature conversion running at 1 Hz. The second one was the additional CPU load caused by the complex functionality of the existing D/3 system. Here it was underestimated that each digital and analog input and output channel had it’s own alarm limits in the D/3 system.In a SCADA like system as Cube the base functionality of a channel is to read the value and make it available to the system. Any additional functionality must be added. Last not least the load on the network for polling all the alarm limits –typically for a SCADA system –was also driving the network to it’s limits.Finally the contract with Orsi was cancelled and an upgrade of the D/3 system was the only possible solution. It was finally carried out in march 2003.In any case it should be mentioned that the Cube approach had the advantage of a homogeneous configuration environment (for the Cube front end controllers) –compared with heterogeneous environments for ‘pure’ SCADA systems.SCADA (PVSS-II)The H1 experiment at the HERA accelerator decided to use PVSS-II for an upgrade of their slow control systems[3].The existing systems were developed by several members of the H1 collaboration and were difficult to maintain. The decision to use PVSS as a WordStrment was driven by the results of an extensive survey carried out at CERN by the Joint Controls Project [4]. PVSS is a ‘pure’ Supervisory And Data Acquisition System (SCADA). It provides a set of drivers for several field buses and generic socket libraries to implement communication over TCP/IP. The core element is the so called event manager. It collects the data (mostly by polling) from the I/O devices and provides an event service to the attached management services like: control manager, database manager, user interface, API manager and the built in HTTP server. The PVSS scripting library allows to implement complex sequences as well as complex graphics.Compared with other SCADA systems PVSS comes with one basic feature: it provides a true object oriented API to the device’s data.One major disadvantage of SCADA systems is the fact that two databases, the one for the PLC and the one for the SCADA system must be maintained. Integrated environments try to overcome this restriction.EPICSEPICS has emerged at DESY from a problem solver to a fully integrated control system. Starting from the data collector and number cruncher for the cryogenic control system, EPICS made it’s way to become the core application for the DESY utility group. In addition it is used wherever data is available through VME boards or by means of Industry Pack (IP) modules. For those cryogenic systems which are not controlled by the D/3 system EPICS is used with it’s complete functionality. In total about 50 Input Output Controller (IOC) are operational processing about 25 thousand records.1 EPICS as a SCADA SystemThe utility group ( water, electrical power, compressed air, heating and air conditioning) is using a variety of PLC’s spread out over the whole DESY site. EPICS is used to collect the data from these PLC’s over Profibus (FMS and DP) and over Ethernet (Siemens H1 and TCP). The IOC’s provide the interfaces to the buses and collect the data. The built in alarm checking of the EPICS records is used to store and forward alarm states to the alarm handler (alh) of the EPICS toolkit. In addition tools like the channel archiver and the graphic display (dm2k) are used. The default name resolution (by UDP broadcast) and the directory server (name server) are used to connectclient and server applications over TCP. All of these are basically SCADA functions.The textual representation of all configuration files ( for the IOC, the graphic tool, the alarm handler and the archiver) provides a flexible configuration scheme. At DESY the utility group has developed a set of tools to create IOC databases and alarm configuration files from Oracle. Thisway the controls group provides the service to maintain the EPICS tools and the IOC’s while the users can concentrate on the equipment being controlled.2 EPICS as a DCS SystemBesides the basic components of a SCADA system EPICS also provides a full flavoured Input Output Controller (IOC).The IOC provides all of the function a DCS system requires, such as: a standard set of properties implemented in each record, built in alarm checking processed during the execution of each record; control records like PID etc.;configuration tools for the processing engine. The flexible naming scheme and the default display and alarm properties for each record ease the connection between the operator tools and the IOC’s. The flexible data acquisition supports the poll mode as well as the publish subscribe mode. The latter reduces the traffic drastically.PLC’sPLC’s provide nowadays the same rich functionality as it was known from stand alone control systems in the past.Besides the basic features like the periodic execution of a defined set of functions they also allow extensive communication over Ethernet including embedded http servers and different sets of communication programs.Besides the communication processors, display processors can be linked to PLC’s to provide local displays which can be comprised as touch panels for operator intervention and value settings.These kind of PLC’s are att ractive for turn key systems which are commissioned at the vendors site and later integrated into the customers control system.Intelligent I/ONew developments in I/O devices allow to ‘cluster’ I/O in even smaller groups and connect theses clustered I/O channels directly to the control system. PLC’s are not any more necessary for distributed I/O. Simple communication processors for any kind of field buses or for Ethernet allow an easy integration into the existing controls infrastructure.Little local engines can run IEC 61131 programs. Thedifferences between PLC’s and intelligent I/O subsystems fade away.FUNCTIONALITYThe ever lasting question why control systems for accelerators and other highly specialized equipment are often home grown or at least developed in a collaboration but only in rare cases commercial shall not be answered here. We try to summarize here basic functionalities of different controls approaches.Front-end ControllerOne of the core elements of a control system is the front-end controller. PLC’s can be used to implement most of the functions to control the equipment. The disadvantage is the complicated access to the controls properties. For instance all of the properties of a control loop like the P, I and D parameter, but also the alarm limits and other additional properties must be addressed individually in order to identify them in the communication protocol and last not least in the display-, alarm- and archive programs. In addition any kind of modifications of these embedded properties is difficult to track because two or more systems are involved. This might be one strong argument why control loops are mainly implemented on the IOC level rather than PLC’s.1 I/O and Control LoopsComplex control algorithms and control loops are the domain of DCS alike control systems. The support for sets of predefined display and controls properties is essential. If not already available (like in DCS systems) such sets of generic properties are typically specified throughout a complete control system (see namespaces).2 Sequence/ State programsSequence programs can run on any processor in a control system. The runtime environment depends on the relevance of the code for the control system. Programs fulfilling watchdog functions have to run on the front-end processor directly. Sequence programs for complicated startup and shutdown procedures could be run on a workstation as well.The basic functionality of a state machine can be even implemented in IEC 61131. Code generators can produce ‘C’ code which can be compiled for the runtime environment.3 Supported HardwareThe support for field buses and Ethernet based I/O is a basic functionality for SCADA type systems it is commercially available from any SCADA system on the market. The integration of specific hardware with specific drivers and data conversion is the hard part in a commercial environment. Open API’s or scripting support sometimes help to integrate custom hardware. If these tools are not provided for the control system it is difficult –if not impossible - to integrate custom hardware.New industrial standards like OPC allow the communication with OPC aware devices and the communication between control systems. One boundary condition for this kind of functionality is the underlying operating system. In the case of OPC it is bound to DCOM which is a Microsoft standard. UNIX based control systems have a hard time to get connected. Only control systems supporting multiple platforms can play a major role in a heterogeneous environments.As a result the limited support for custom- or specialized hardware may give reason for the development of a new control system.Display and OperationBesides the front-end system the operator interfaces play a major role for the acceptance of a control system. SCADA tools come with a homogeneous look and feel throughout their set of tools. Toolkits implemented in a collaboration might vary because the individual tools were developed by different teams.1 GraphicSynoptic displays are the advertising sign for any control system. Commercial synoptic displays come with a rich functionality and lots of special features. Starting to make use of all these features one will find out that all individualproperties of the graphic objects must be specified individually. Since SCADA systems must be generic they cannot foresee that an input channel does not only consist ofa value but also consists of properties like display ranges andalarm values. Defining all of these properties again and again can be a pretty boring job. Some systems allow to generate prototypes of graphic objects. These prototype or template graphics are complex and need a specialist to generate them.DCS or custom synoptic display programs can make use of the common set of properties each I/O point provides. This predefined naming scheme will fill in all standard property values and thus only require to enter the record – or device name into the configuration tool. A clear advantage for control systems with a notion of I/O objects rather than I/O points.2 AlarmingAlarms are good candidates to distinguish between different control system architectures. Those systems which have I/O object implemented also provide alarm checking on the front-end computer. Those systems which only know about I/O points have to add alarm checking into the I/O processing. While the I/O object approach allows to implement alarm checking in the native programming language of the front-end system, I/O point oriented systems typically have to implement this functionality in their nativescripting language. This is typically less efficient and error prone because all properties must be individually configured.This leads to a flood of properties. Not only the error states for each I/O point wind up to be individual I/O points but also the alarm limits and the alarm severity of each limit must be defined as I/O points if it is desired to be able to change their values during runtime.Besides this impact on the configuration side the processing and forwarding of alarms makes the difference between SCADA and DCS systems. Since SCADA systems inherently do not ‘know’ about alarms, each alarm state must be polled either directly from the client application or in advanced cases from an event manager which will forward alarm states to the clients. In any case a lot of overhead for ‘just’ checking alarm limits. DCS system again have the advantage that clients can either register themselves for alarm states und thus get the information forwarded or are configured to send alarmchanges to certain destinations spread around the control system. The latter case is only possible for systems which in total are configured with all the nodes taking part in the controls network.3 Trending and ArchivingTrending has become an important business in control systems architectures. Trends are necessary to trace error conditions or for post mortem and performance analysis of the controlled plant. Besides some custom implementations which are capable to store the data of complete control objects, most of the trending tools archive scalar data.Additional features like conditional trending or correlation plots make up the difference between individual implementations.4 Programming InterfacesWith respect to open programming interfaces PLC’s and DCS systems have a common strategy. They are running reliably because there’s no way to integrate custom code which could interfere with the internal processing. As a consequence the customer has to order ‘specials’ - which are extremely expensive – or forget about it and use the system as a black box.Since SCADA systems by definition must be able to communicate with a variety of I/O subsystems they already have some built in API’s which allow to integrate custom functionality.Specially collaborative systems need a certain openness to fulfill all the requirements from various development groups.Programming interfaces on all levels like font-end I/O, front-end processing, networking etc. are mandatory. A clear advantage for this type of system.5 RedundancyIf redundancy means the seamless switch which takes over all the states and all the values of the I/O and all states of all programs currently running, it is a domain of only a few DCS systems. Custom or CCS implementation do not provide this kind of functionality. Maybe because of the immense effort and the fact that it is only required in rare cases.Besides processor redundancy, redundant networks or I/O subsystems are available for certain commercial DCS systems. Again – a domain which is not covered by SCADA or CCS implementations.Advanced safety requirements may be covered byredundant PLC subsystems. These are for instance installed in (nuclear) power plants. Requirements for Personal Protection Systems (PPS) can sometimes only be fulfilled by redundant PLC’s. In process controls redundant PLC’s are only used in rare cases.6 NamespaceThe flat namespace of SCADA systems has already been described in the alarm section. Some SCADA systems (like PVSS-II) provide the notion of control objects or structured data which is a rare case. In all other cases so called field objects must be specified. These are objects which consist ofa list of properties (implemented as I/O points) and a set ofmethods ( implemented asmacros or function calls). One of these approaches is the UniNified Industrial COntrol System (UNICOS) at CERN [5].DCS systems and most of the custom/ collaborative systems are record –or device oriented. The difference being that typically one record is connected to a single I/O point and provides this way all sub features of a record implementation like individual engineering units, display- and alarm limits. The device oriented approach allows to connect several I/O points. The major difference being the fact that an object oriented device implementation provides methods and states for a device while (EPICS) records only serve a certain set of built in functions.Naming hierarchies are not specific to a type of implementation. They are available for some systems of any kind. For sure hierarchical naming schemes are desirable.IMPLEMENTATION STRATEGIESAfter having shown all the possible controls approaches it is time to have a look at the implementation of control systems.Starting from the I/O level one has to decide whether commercial solution are required, feasible or wanted.Special I/O does not always require custom solution for the font-end controller. Signals can be converted into standard signals but this does not apply for all kinds of signals.Resolution, repetition rates and signal levels might require custom developments which must be integrated into the overall control architecture. Even if the signals can not beconnected to standard I/O interfaces it might be possible to develop I/O controllers which implement a field bus interface which allow the integration with commercial control systems. Once this level of integration is not possible custom front-end controllers like VME crates come into play.Besides the decision whether special I/O requires dedicated custom solutions one has to decide who will do which part of the work? Does for instance the necessity of VME crates prohibit the delivery of a ‘turn key’ system built by industry?Or does a PLC based front-end system require a commercial SCADA system for high level controls?Turn Key SystemsIt is a clear trend in industry to deliver turn key systems. It allows a modular design of the whole system. Individual components can be subcontracted to several companies and tested locally. Once delivered to the construction site the primary acceptance tests have already been passed and the second phase, to integrate the subsystem into the global control system begins.While the detailed specification of control loops etc. is now part of the subsystems contract, the customer has to specify clearly how much information of the subsystem must be made available, what the data structures will look like and which connection (field bus/ Ethernet) will be used.Most turn key systems are delivered with PLC’s. The construction of the Swiss Light Source (SLS) has shown that also a VME based I/O system running a CCS – in this case EPICS – can be successfully commissioned [6].PLC Based SystemsPLC based systems are a consequence of the turn key ansatz. The next obvious approach might be to look besides commercial PLC’s also for commercial SCADA systems.The advantage is clearly the same like for the PLC: stable software, no programming – only configuration, support and good documentation. At DESY we have successfully established a relation between the controls group which provides a CCS service based on EPICS and the utility group which uses the EPICS configuration tools to set up their control environment. The big advantage though beingthat the EPICS code can be adjusted to the special requirements from both sides.Industrial SolutionsThe difference between CCS solutions and commercial solutions is fading away as soon as industry starts to deliver and support collaborative control systems. At KEK a company was contracted to supply programmers for the KEK-B upgrade. These programmers were trained in writing drivers and application code for EPICS. As a result the KEK-B control system is a mixture of software developed partly by industry and partly in house. This is another example for an industrial involvement for a CCS implementation.COSTThe question: “Was is the total cost of ownership (TCO) ofa PC?” has kept people busy since PC’s exist. The answersvary to all extremes. The question what is the TCO of a control system might give similar results.If you go commercial you have to pay for the initial licenses the implementation which is typically carried out by the supplier or by a subcontractor, and you pay for the on going software support which might or might not include the update license fee.If you go for a collaborative approach, you might contract a company or implement everything on your own. A question of ‘time and money’ as industry says. You will have more freedom and flexibility for your implementations but also a steeper learning curve. You can rely on the collaboration to provide new features and versions or you can contribute yourself. A major difference calculating the long term costs for a control system.At DESY one can roughly estimate that the (controls application)-support for a commercial approach – here D/3 - and the -support for a collaborative approach – here EPICS - is nearly the same. The software support and upgrade license fee is equivalent to one and a half FTE’s – which is about the manpower necessary to support new hardware and to upgrade EPICS.CONCLUSIONSDepending on the size and the requirements for a controls project the combination of commercial solutions and solutions based on a collaborative approach is possible in any rate between 0 and 100 percent. This applies for all levels from implementation to long term support. Special requirements on safety issues or a lack of manpower might turn the scale commercial. The necessity to interface special hardware, special timing requirements, the ‘having the code in my hands’ argument or the initial costs for commercial solutions will turn the scale collaborative. As long as collaborative approaches like EPICS stay up to date and run as stable and robust as commercial solutions, both will keep their position in the controls world in a complementary symbiosis.外文资料翻译外文翻译译文工业控制系统和协同控制系统现今的控制系统被广泛运用于许多领域.从纯真的工业控制系统到协同控制系统（CCS），控制系统不竭变动，不竭升级，现在则趋向于家庭控制系统，而它则是这两者的变种.被应用的控制系统的种类取决于技术要求.而且，实践标明，经济和社会因素也对此很重要.任何决建都有它的优缺点.工业控制要求可靠性，完整的文献记载和技术支持.经济因素使决定趋向于协同工具.能够亲自接触源码并可以更快速地解决问题是家庭控制系统的要求.多年的把持经验标明哪个解决方法是最主要的不重要，重要的是哪个可行.由于异类系统的存在，针对分歧协议的支持也是至关重要的.本文介绍工业控制系统，PlC controlled turn key系统，和CCS 工具，以及它们之间的把持.引言：80年代早期，随着为HERA(Hadron-Elektron-Ring-Anlage)加速器装置高温控制系统，德国电子同步加速器研究所普遍开始研究过程控制.这项新技术是必需的，因为可是现有的硬件没有能力来处置标准过程控制信号，如4至20毫安的电流输入和输出信号.而且软件无法在秒的稳定重复率下运行PID控制回路.另外，在实现对复杂的高温冷藏系统的开闭过程中，频率项目显得尤为重要.有需要增加接口解决总线问题并增加运算能力，以便于高温控制.因为已装置的D / 3系统[1] 只提供了与多总线板串行连接，以实现DMA与VME的连接并用其模拟多总线板的功能.温度转换器的计算功能来自一个摩托罗拉MVME 167 CPU和总线适配器，以及一个MVME 162 CPU.其把持系统是VxWorks，而应用法式是EPICS.由于对它的应用相当胜利，其还被运用于正在寻找一个通用的解决方案以监督他们的分布式PLC的公共事业管理.德国电子同步加速器研究所对过程管理系统的筛选集散控制系统（D/ 3）：市场调查标明：来自GSE的D / 3系统被HERA高温冷藏工厂选中.因为集散控制系统（D/ 3）的特性，所以这决定很不错.在展示端和I / O端扩展此系统的可能将有助于解决日益增加的HERA试验控制的要求.制约系统的年夜小的因素不是I / O的总数，通信网络的疏通与否.而通信网络的疏通与否取决于不存档的数据总量，不取决于报警系统中配置的数据.拥有DCS特点（Cube）的SCADA系统：相对Y2K问题促使我们寻找一个升级版或者取代版来取代现有的系统而言，以上提到的D / 3系统有一些硬编码的限制.由于急需给Orsi公司提供他们的产物，Cube开始起作用了[2].该项目包括装置功能的完全更换.这包括D / 3，以及德国电子同步加速器研究所的集成总线SEDAC和VME的温度转换器.该项目很有前景.可是因为HERA试验原按时间是有限制的，所以技术问题和组织问题也迫使计划提前.在供应商网站上的最后验收测试又呈现了戏剧性的性能问题.有两个因素引起了这些问题.第一个跟低估在1赫兹运行的6级温度转换器的CPU负荷有关.第二个由现有D / 3系统复杂的功能造成的额外负荷引起的.每个数字和模拟输入和输出通道在D / 3系统里的自身报警限值也被低估了.所有的附加功能都必需添加进去.最后，所有网络负载的报警限值，尤其是SCADA系统，也促使网络生成了限制.最后，与Orsi公司的合同被取消了.升级的D / 3系统是唯一可能的解决法子.在2003年3月，此系统最后被付诸实践.现在，相比“纯洁”SCADA系统的异质环境，Cube有同质配置环境的优势.SCADA（PVSS -Ⅱ）：在HERA加速器上的H1实验中，实验人员为升级他们的低速控制系统，决定使用PVSS -Ⅱ.现有的系统是由H1合作组的几名成员开发的，而现在却难以维持了.在CERN由联合控制项目[4]进行的广泛调查促使他们做出使用PVSS作为取代品的决定.PVSS是一个“纯洁”的监控和数据收集系统（SCADA系统）.其核心元素叫做事件管理器.它收集的数据主要是由I/ O设备提供.它还提供附加的管理服务，如：控制经理，数据库管理，用户界面，API经理以及在建的HTTP服务器.该PVSS脚本库允许执行复杂的序列以及复杂的图形.相比其他SCADA系统PVSS带有一个基本特点：它提供了API给设备的数据.SCADA系统的一个主要缺点是其中的两个数据库，一个为PLC’s服务，另一个为SCADA系统服务，这两个数据库必需维持.集成环境将努力克服这个限制.EPICS：在德国电子同步加速器研究所，EPICS从问题解决系统演化成了全集成控制系统.从成为高温控制系统的数据收集器和数量控制器，EPICS成了德国电子同步加速器研究所公用事业集团使用的核心系统.另外，通过 Industry Pack（IP）模块的手段，它还能运用于通过VME板卡的任何数据.EPICS通过其完整的功能，运用于没有由D / 3系统控制的高温冷藏系统.所有年夜约50个输入输出控制器运作年夜约25000业务处置记录.作为一个SCADA系统的EPICS：该公共事业组（水，电，压缩空气，加热和调温）使用各种散布在整个德国电子同步加速器研究所网站上的PLC.IOC向客户提供接口并收集数据.另外，如通道归档和图形显示（dm2k）会被使用.默认名决议和目录服务器（域名服务器）用于连接在TCP客户端和服务器应用法式.所有这些都是基本的SCADA功能.所有的配置文件（图形工具，报警处置法式和归档）提供了一种灵活的配置方案.德国电子同步加速器研究所公用事业集团已制定了一套工具来创立IOC数据库和配置文件.这样，控制组提供的服务坚持EPICS工具，而用户可以精力集中在被控制的设备上了.作为一个DCS系统的EPICS：作为SCADA系统的基本组成部份，EPICS还提供完整的输入输出控制器（IOC）.IOC提供所有功能DCS系统要求，如：实施每个记录的标准的属性；执行每个记录时的报警检查过程；控制记录，如PID.灵活的命名方案，默认的显示和每个记录的报警属性缓和了运作工具和IOC之间的连接.灵活的数据收集模式，支持调查模式以及发布定阅模式.。
PLC概述外文文献翻译、中英文翻译、外文翻译
外文原文：ONE、PLC overviewProgrammable controller is the first in the late 1960s in the United States, then called Plc programmable logic controller (Programmable Logic Controller) is used to replace relays. For the implementation of the logical judgment, timing, sequence number, and other control functions. The concept is presented Plc General Motors Corporation. Plc and the basic design is the computer functional improvements, flexible, generic and other advantages and relay control system simple and easy to operate, such as the advantages of cheap prices combined controller hardware is standard and overall. According to the practical application of target software in order to control the content of the user procedures memory controller, the controller and connecting the accused convenient target.In the mid-1970s, the Plc has been widely used as a central processing unit microprocessor, import export module and the external circuits are used, large-scale integrated circuits even when the Plc is no longer the only logical (IC) judgment functions also have data processing, PID conditioning and data communications functions. International Electro technical Commission (IEC) standards promulgated programmable controller for programmable controller draft made the following definition : programmable controller is a digital electronic computers operating system, specifically for applications in the industrial design environment. It used programmable memory, used to implement logic in their internal storage operations, sequence control, timing, counting and arithmetic operations, such as operating instructions, and through digital and analog input and output, the control of various types of machinery or production processes. Programmable controller and related peripherals, and industrial control systems easily linked to form a whole, to expand its functional design. Programmable controller for the user, is a non-contact equipment, the procedures can be changed to change production processes. The programmable controller has become a powerful tool for factory automation, widely popular replication. Programmable controller is user-oriented industries dedicated control computer, with many distinctive features.First, high reliability, anti-interference capability;Second，programming visual, simple;Third, adaptability good;Fourth functional improvements, strong functional interface.TWO、History of PLCProgrammable Logic Controllers (PLC), a computing device invented by Richard E. Morley in 1968, have been widely used in industry including manufacturing systems, transportation systems, chemical process facilities, and many others. At that time, the PLC replaced the hardwired logic with soft-wired logic or so-called relay ladder logic (RLL), a programming language visually resembling the hardwired logic, and reduced thereby the configuration time from 6 months down to 6 days [Moody and Morley, 1999].Although PC based control has started to come into place, PLC based control will remain the technique to which the majority of industrial applications will adhere due to its higher performance, lower price, and superior reliability in harsh environments. Moreover, according to a study on the PLC market of Frost and Sullivan [1995], an increase of the annual sales volume to 15 million PLCs per year with the hardware value of more than 8 billion US dollars has been predicted, though the prices of computing hardware is steadily dropping. The inventor of the PLC, Richard E Morley, fairly considers the PLC market as a 5-billion industry at the present time.Though PLCs are widely used in industrial practice, the programming of PLC based control systems is still very much relying on trial-and-error. Alike software engineering, PLC software design is facing the software dilemma or crisis in a similar way. Morley himself emphasized this aspect most forcefully by indicating`If houses were built like software projects, a single woodpecker could destroy civilization.”Particularly, practical problems in PLC programming are to eliminate software bugs and to reduce the maintenance costs of old ladder logic programs. Though the hardware costs of PLCs are dropping continuously, reducing the scan time of the ladder logic is still an issue in industry so that low-cost PLCs can be used.In general, the productivity in generating PLC is far behind compared to other domains, for instance, VLSI design, where efficient computer aided design tools are in practice. Existent software engineering methodologies are not necessarily applicable to the PLC based software design because PLC-programming requires a simultaneous consideration of hardware and software. The software design becomes, thereby, more and more the major cost driver. In many industrial design projects, more than of the manpower allocated for the control system design and installation is scheduled for testing and debugging PLC programs.In addition, current PLC based control systems are not properly designed to support the growing demand for flexibility and reconfigurability of manufacturing systems. A further problem, impelling the need for asystematic design methodology, is the increasing software complexity in large-scale projects.The objective of this thesis is to develop a systematic software design methodology for PLC operated automation systems. The design methodology involves high-level description based on state transition models that treat automation control systems as discrete event systems, a stepwise design process, and set of design rules providing guidance and measurements to achieve a successful design. The tangible outcome of this research is to find a way to reduce the uncertainty in managing the control software development process, that is, reducing programming and debugging time and their variation, increasing flexibility of the automation systems, and enabling software reusability through modularity. The goal is to overcome shortcomings of current programming strategies that are based on the experience of the individual software developer.Three、now of PLCFrom the structure is divided into fixed PLC and Module PLC, the two kinds of PLC including CPU board, I/O board, display panel, memory block, power, these elements into a do not remove overall. Module type PLC including CPU module, I/O modules, memory, the power modules, bottom or a frame, these modules can be according to certain rules combination configuration.In the user view, a detailed analysis of the CPU's internal unnecessary, but working mechanism of every part of the circuit. The CPU control works, by it reads CPU instruction, interprets the instruction and executes instructions. But the pace of work by shock signal control.Unit work under the controller command used in a digital or logic operations.In computing and storage register of computation result, it is also among the controller command and work. CPU speed and memory capacity is the important parameters fot PLC . its determines the PLC speed of work, IO PLC number and software capacity, so limits to control size. Central Processing Unit (CPU) is the brain of a PLC controller. CPU itself is usually one of the microcontrollers. Aforetime these were 8-bit microcontrollers such as 8051, and now these are 16-and 32-bit microcontrollers. Unspoken rule is that you’ll find mostly Hitachi and Fujicu microcontrollers in PLC controllers by Japanese makers, Siemens in European controllers, and Motorola microcontrollers in American ones. CPU also takes care of communication, interconnectedness among other parts of PLC controllers, program execution, memory operation, overseeing input and setting up of an output.System memory (today mostly implemented in FLASH technology) is used by a PLC for a process control system. Aside form. this operating systemit also contains a user program translated forma ladder diagram to a binary form. FLASH memory contents can be changed only in case where user program is being changed. PLC controllers were used earlier instead of PLASH memory and have had EPROM memory instead of FLASH memory which had to be erased with UV lamp and programmed on programmers. With the use of FLASH technology this process was greatly shortened. Reprogramming a program memory is done through a serial cable in a program for application development.User memory is divided into blocks having special functions. Some parts of a memory are used for storing input and output status. The real status of an input is stored either as “1”or as “0”in a specific memory bit/ each input or output has one corresponding bit in memory. Other parts of memory are used to store variable contents for variables used in used program. For example, time value, or counter value would be stored in this part of the memory.PLC controller can be reprogrammed through a computer (usual way), but also through manual programmers (consoles). This practically means that each PLC controller can programmed through a computer if you have the software needed for programming. Today’s transmission computers are ideal for reprogramming a PLC controller in factory itself. This is of great importance to industry. Once the system is corrected, it is also important to read the right program into a PLC again. It is also good to check from time to time whether program in a PLC has not changed. This helps to avoid hazardous situations in factory rooms (some automakers have established communication networks which regularly check programs in PLC controllers to ensure execution only of good programs).Almost every program for programming a PLC controller possesses various useful options such as: forced switching on and off of the system input/outputs (I/O lines), program follow up in real time as well as documenting a diagram. This documenting is necessary to understand and define failures and malfunctions. Programmer can add remarks, names of input or output devices, and comments that can be useful when finding errors, or with system maintenance. Adding comments and remarks enables any technician (and not just a person who developed the system) to understand a ladder diagram right away. Comments and remarks can even quote precisely part numbers if replacements would be needed. This would speed up a repair of any problems that come up due to bad parts. The old way was such that a person who developed a system had protection on the program, so nobody aside from this person could understand how it was done. Correctly documented ladder diagram allows any technician to understand thoroughly how system functions.Electrical supply is used in bringing electrical energy to central processing unit. Most PLC controllers work either at 24 VDC or 220 VAC. On some PLC controllers you’ll find electrical supply as a separatemodule. Those are usually bigger PLC controllers, while small and medium series already contain the supply module. User has to determine how much current to take from I/O module to ensure that electrical supply provides appropriate amount of current. Different types of modules use different amounts of electrical current.This electrical supply is usually not used to start external input or output. User has to provide separate supplies in starting PLC controller inputs because then you can ensure so called “pure” supply for the PLC controller. With pure supply we mean supply where industrial environment can not affect it damagingly. Some of the smaller PLC controllers supply their inputs with voltage from a small supply source already incorporated into a PLC.Four、PLC design criteriaA systematic approach to designing PLC software can overcome deficiencies in the traditional way of programming manufacturing control systems, and can have wide ramifications in several industrial applications. Automation control systems are modeled by formal languages or, equivalently, by state machines. Formal representations provide a high-level description of the behavior of the system to be controlled. State machines can be analytically evaluated as to whether or not they meet the desired goals. Secondly, a state machine description provides a structured representation to convey the logical requirements and constraints such as detailed safety rules. Thirdly, well-defined control systems design outcomes are conducive to automatic code generation- An ability to produce control software executable on commercial distinct logic controllers can reduce programming lead-time and labor cost. In particular, the thesis is relevant with respect to the following aspects.In modern manufacturing, systems are characterized by product and process innovation, become customer-driven and thus have to respond quickly to changing system requirements. A major challenge is therefore to provide enabling technologies that can economically reconfigure automation control systems in response to changing needs and new opportunities. Design and operational knowledge can be reused inreal-time, therefore, giving a significant competitive edge in industrial practice.Studies have shown that programming methodologies in automation systems have not been able to match rapid increase in use of computing resources. For instance, the programming of PLCs still relies on a conventional programming style with ladder logic diagrams. As a result, the delays and resources in programming are a major stumbling stone for the progress of manufacturing industry. Testing and debugging may consume over 50% of the manpower allocated for the PLC program design. Standards[IEC 60848, 1999; IEC-61131-3, 1993; IEC 61499, 1998; ISO 15745-1, 1999] have been formed to fix and disseminate state-of-the-art design methods, but they normally cannot participate in advancing the knowledge of efficient program and system design.A systematic approach will increase the level of design automation through reusing existing software components, and will provide methods to make large-scale system design manageable. Likewise, it will improve software quality and reliability and will be relevant to systems high security standards, especially those having hazardous impact on the environment such as airport control, and public railroads.The software industry is regarded as a performance destructor and complexity generator. Steadily shrinking hardware prices spoils the need for software performance in terms of code optimization and efficiency. The result is that massive and less efficient software code on one hand outpaces the gains in hardware performance on the other hand. Secondly, software proliferates into complexity of unmanageable dimensions; software redesign and maintenance-essential in modern automation systems-becomes nearly impossible. Particularly, PLC programs have evolved from a couple lines of code 25 years ago to thousands of lines of code with a similar number of 1/O points. Increased safety, for instance new policies on fire protection, and the flexibility of modern automation systems add complexity to the program design process. Consequently, the life-cycle cost of software is a permanently growing fraction of the total cost. 80-90% of these costs are going into software maintenance, debugging, adaptation and expansion to meet changing needs.Today, the primary focus of most design research is based on mechanical or electrical products. One of the by-products of this proposed research is to enhance our fundamental understanding of design theory and methodology by extending it to the field of engineering systems design.A system design theory for large-scale and complex system is not yet fully developed. Particularly, the question of how to simplify a complicated or complex design task has not been tackled in a scientific way. Furthermore, building a bridge between design theory and the latest epistemological outcomes of formal representations in computer sciences and operations research, such as discrete event system modeling, can advance future development in engineering design.From a logical perspective, PLC software design is similar to the hardware design of integrated circuits. Modern VLSI designs are extremely complex with several million parts and a product development time of 3 years [Whitney, 1996]. The design process is normally separated into a component design and a system design stage. At component design stage, single functions are designed and verified. At system design stage, components are aggregated and the whole system behavior and functionality is tested through simulation. In general, a complete verification isimpossible. Hence, a systematic approach as exemplified for the PLC program design may impact the logical hardware design.Five、AK 1703 ACPFollowing the principle of our product development, AK 1703 ACP has high functionality and flexibility, through the implementation of innovative and reliable technologies, on the stable basis of a reliable product platform.For this, the system concept ACP (Automation, Control and Protection) creates the technological preconditions. Balanced functionality permits the flexible combination of automation, telecontrol and communication tasks. Complemented with the scalable performance and various redundancy configurations, an optimal adaptation to the respective requirements of the process is achieved.AK 1703 ACP is thus perfectly suitable for automation with integrated telecontrol technology as:• Telecontrol substation or central device• Auto mation unit with autonomous functional groups• Data node, station control device, front-end or gateway• With local or remote peripherals• For rear panel installation or 19 inch assembly• Branch-neutral product, therefore versatile fields of application and high productstability• Versatile communication• Easy engineering• Plug & play for spare parts• Open system architecture• Scalable redundancy• The intelligent terminal - TM 1703The Base Unit AK 1703 ACP with Peripheral Elements has one basic system element CP-2010/CPC25 (Master control element) and CP-2012/PCCE25 (Processing and communication element) ,one bus line with max. 16 peripheral elements can be connected.CP-2010/CPC25 Features and FunctionsSystem Functions:• Central element,coordinating all system servicesCentral hub function for all connected basic system elements• Time managementCentral clock of the automation unitSetting anf keeping the own clock`s time with a resolution of 10ms Synchronization via serid communication via LAN or local• RedundancyVoting and change-over for redundant processing and communication elements of the own automation unitSupports voting and change-over by an external SCA-RS redundancy switchSupports applicational voting and change-over by an exterual system,e.g.a control system• SAT TOLLBOX|| connectionStoring firmware and parameters on a Flash CardCommunication:• Communication via installable protocol elements to any superior or subordinate automation unit• Automatic data flow routing• Priority based data transmission (priority control)•Own circular buffer and process image for each connected station(data keeping)• Redundant communication routesCommunication with redundant remote stations• Special application specific functions for dial-up trafficTest if stations are reachableProcess Peripherals:• Tansmission of spontaneous information objects from and to peripheral elements, via the serial Ax 1703 peripheral bus Functions for Automatoin:• Open-/closed-loop control function for the execution of freely definable user programs which are created with CAEX plus according to IEC 61131-3,ing function diagram technology512KB for user programApprox 50.000 variables and signals,2.000 of them retainedCycle of 10ms or a multiphe thereofOnline testLoadable without service interruption• Redundant open-/closed-loop control functionsSynchronization via redundancy linkTransmission of periodic process information between theopen-/closed-loop control function and the peripheral elements,via the serial Ax 1703 peripheral busSIX、SIEMENS PLCSIMATIC S7-300 series PLC applied to all walks of life and various occasions in the detection, monitoring and control of automation, its power to both the independent operation of, or connected to a network able to achieve complex control.The photoelectric products with isolation, high electromagnetic compatibility; have high industrial applicability, allowing the ambient temperature of 60 ℃; has strong anti-jamming and anti-vibration and impact resistance, so in a harsh working environment has been widely Applications.I also mean freedom of communication S7-300 type PLC' s a very unique feature, which allows S7-300-PLC can deal openly with any other communications equipment, communications controller, or PLC S7-300 type can be defined by the user's own Communications protocol (of the agreement ASCII), the baud rate to 1.5 Mbit / s (adjustable). So that can greatly increase the scope of communications so that the control system configuration more flexible and convenient. Of any kind with a serial interface peripherals, such as: printers or bar code readers, Drives, a modem (Modem), the top PC-connected, and so can be used. Users can program to develop communication protocols, the exchange of data (for example: ASCII character code), RS232 interfaces with the equipment can also be used PC / PPI cable linking the free communication communications.When the PC offline, under the control of the next crew, the whole system can operate normally.PC that is by control centre, mainly by the PC and laser printer components, using SIMATIC WINCC software platform, the all-Chinese interface, friendly man-machine dialogue. Managers and operators can be observed through a PC, shown in the various kinds of information to understand the present and past the ice-storage operation of the automatic control system and all the parameters, and through the mouse to print equipment management and implementation tasks.WINCC software in the field of automation can be used for all the operators’ control and monitoring tasks. Can be controlled in the process of the events clearly show, and shows the current status and order records, the recorded data can show all or select summary form, or may be required for editing, printing and output statements and trends .WINCC able to control the critical situation in the early stages of the report, and the signal can be displayed on the screen, can also use sound to be felt. It supported by online help and operational guidelines to eliminate failure. WINCC a workstation can be devoted to the process control to the process so that important information not is shielded. Software-assisted operation strategy ensures that the process was not illegal to visit and to provide for non-industrial environment in the wrong operation.WINCC is MICRSOFT WINDOWS98 or WINDOWS NT4.0 operating system, running on a PC object-oriented class 32-bit applications, OLE through the window and ODBC standard mechanism, as an ideal partner to enter the communications world WINDOWS, it can be easily WINCC To integrate a company-wide data processing system.Seven、CommunicationsCommunications are vital to an individual automation cell and to the automated factory as a whole. We've heard a lot about MAP in the last few years, and a lot of companies have jumped on the band wagon. Many, however were disappointed when a fully-defined and completed MAP specification didn’t appear immediately. Says Larry Kumara:”Right now , MAP is still a moving target for the manufacturers specification that is not final. Presently, for example, people are introducing products to meet the MAP 2.1standard.Yet 2.1-based products will be obsolete when the new standard for MAP,3.0is introduced.”Because of this, many PLC vendors are holding off on full MAP implementations. Omron, for example , has an ongoing MAP-compatibility program, but Frank Newborn, vice president of Omron’s Industrial Division, reports that because of the lack of a firm definition, Omron's PLCs don't yet talk to MAP.Since it’s unlikely that an individual PLC would talk to broadband MAP anyway, makers are concentrating n proprietary networks. According to Sal Provanzano, users fear that if they do get on board and vendors withdraw from MAP, they ‘ll pulse width modulation control system be the ones left holding a communications structure that’s not supported.译文：一、PLC概述可编程控制器是60年代末在美国首先出现的，当时叫可编程逻辑控制器PLC（Programmable Logic Controller），目的是用来取代继电器。
PLC相关的外文英语文献与翻译
PLC相关的外文英语文献与翻译RelaysThe Programmable Logic ControllerEarly machines were controlled by mechanical means using cams, gears, levers and other basic mechanical devices. As the complexity grew, sodid the need for a more sophisticated control system. This system contained wired relay and switch control elements. These elements were wired as required to provide the control logic necessary for the particular type of machine operation. This was acceptable for a machine that never needed to be changed or modified, but as manufacturing techniques improved and plant changeover to new products became more desirable and necessary, a more versatile means of controlling this equipment had to be developed. Hardwired relay and switch logic was cumbersome and time consuming to modify. Wiring had to be removed and replaced to provide for the new control scheme required. This modification was difficult and time consuming to design and install and any small "bug" in the design could be a major problem to correct since that also required rewiring of the system. A new means to modify control circuitry was needed. The development and testing ground for this new means was the U.S. auto industry. The time period was the late 1960'sand early 1970's and the result was the programmable logic controller,or PLC. Automotive plants were confronted with a change in manufacturing techniques every time a model changed and, in some cases, for changes onthe same model if improvements had to be made during the model year. The PLC provided an easy way to reprogram the wiring rather than actually rewiring the control system.The PLC that was developed during this time was not very easy to program. The language was cumbersome to write and required highlytrained programmers. These early devices were merely relay replacements and could do very little else. The PLC has at first gradually, and in recent years rapidly developed into a sophisticated and highly versatile control system component. Units today are capable of performing complex math functions including numerical integration and differentiation and operate at the fast microprocessor speeds now available. Older PLCs were capable of only handling discrete inputs and outputs (that is, on-off type signals), while today's systems can accept and generate analog voltages第 1 页共7页and currents as well as a wide range of voltage levels and pulsed signals. PLCs are also designed to be rugged. Unlike their personal computer cousin, they can typically withstand vibration, shock, elevated temperatures, and electrical noise to which manufacturing equipment is exposed.As more manufacturers become involved in PLC production and development, and PLC capabilities expand, the programming language is also expanding. This is necessary to allow the programming of these advanced capabilities. Also, manufacturers tend to develop their ownversions of ladder logic language (the language used to program PLCs). This complicates learning to program PLC's in general since one language cannot be learned that is applicable to all types. However, as withother computer languages, once the basics of PLC operation and programming in ladder logic are learned, adapting to the various manufacturers’ devices is not a complicated process. Most system designers eventually settle on one particular manufacturer that produces a PLC that is personally comfortable to program and has the capabilities suited to his or her area of applications.It should be noted that in usage, a programmable logic controller is generally referred to as a “PLC” or “programmable controller”. Although the term “programmable controller” is generally accepted, it is not abbreviated “PC” because the abbreviation “PC” is usually used in reference to a personal computer. As we will see in this chapter, a PLC is by no means a personal computer.Programmable controllers (the shortened name used for programmable logic controllers) are much like personal computers in that the user can be overwhelmed by the vast array of options and configurations available. Also, like personal computers, the best teacher of which one to selectis experience. As one gains experience with the various options and configurations available, it becomes less confusing to be able to select the unit that will best perform in a particular application.The typical system components for a modularized PLC are:1. Processor.The processor (sometimes call a CPU), as in the self contained units, is generally specified according to memory required for the program to beimplemented. In the第 2 页共7页modularized versions, capability can also be a factor. This includes features such as higher math functions, PID control loops and optional programming commands. The processor consists of the microprocessor, system memory, serial communication ports for printer, PLC LAN link and external programming device and, in some cases, the system power supply to power the processor and I/O modules.2. Mounting rack.This is usually a metal framework with a printed circuit board backplane which provides means for mounting the PLC input/output (I/O) modules and processor. Mounting racks are specified according to the number of modules required to implement the system. The mounting rack provides data and power connections to the processor and modules via the backplane. For CPUs that do not contain a power supply, the rack also holds the modular power supply. There are systems in which the processor is mounted separately and connected by cable to the rack. The mounting rack can be available to mount directly to a panel or can be installedin a standard 19" wide equipment cabinet. Mounting racks are cascadable so several may be interconnected to allow a system to accommodate alarge number of I/O modules.3. Input and output modules.Input and output (I/O) modules are specified according to the input and output signals associated with the particular application. These modules fall into the categories of discrete, analog, high speed counter or register types.Discrete I/O modules are generally capable of handling 8 or 16 and,in some cases 32, on-off type inputs or outputs per module. Modules are specified as input or output but generally not both although some manufacturers now offer modules that can be configured with both input and output points in the same unit. The module can be specified as AC only, DC only or AC/DC along with the voltage values for which it is designed.Analog input and output modules are available and are specified according to the desired resolution and voltage or current range. Aswith discrete modules, these are generally input or output; however some manufacturers provide analog input and output in the same module. Analog modules are also available which can directly accept thermocouple inputs 第 3 页共7页for temperature measurement and monitoring by the PLC.Pulsed inputs to the PLC can be accepted using a high speed countermodule. This module can be capable of measuring the frequency of an inputsignal from a tachometer or other frequency generating device. These modules can also count the incoming pulses if desired. Generally, both frequency and count are available from the same module at the same time if both are required in the application.Register input and output modules transfer 8 or 16 bit words of information to and from the PLC. These words are generally numbers (BCD or Binary) which are generated from thumbwheel switches or encoder systems for input or data to be output to a display device by the PLC.Other types of modules may be available depending upon the manufacturer of the PLC and it's capabilities. These include specialized communication modules to allow for the transfer of information from one controller to another. One new development is an I/O Module which allows the serial transfer of information to remote I/O units that can be asfar as 12,000 feet away.4. Power supply.The power supply specified depends upon the manufacturer's PLC being utilized in the application. As stated above, in some cases a power supply capable of delivering all required power for the system is furnished as part of the processor module. If the power supply is a separate module, it must be capable of delivering a current greater than the sum of all the currents needed by the other modules. For systems with the power supply inside the CPU module, there may be some modules in the system which require excessive power not available from the processor either because of voltage or current requirements that can only be achieved through the addition of a second power source. This is generally true if analog or external communication modules are present since these require ? DC supplies which, in the case of analog modules, must be well regulated.5. Programming unit.The programming unit allows the engineer or technician to enter and edit the program to be executed. In it's simplest form it can be a hand held device with a keypad for program第 4 页共7页entry and a display device (LED or LCD) for viewing program steps or functions, as shown. More advanced systems employ a separate personal computer which allows the programmer to write, view, edit and download the program to the PLC. This is accomplished with proprietary software available from the PLC manufacturer. This software also allows the programmer or engineer to monitor the PLC as it is running the program. With this monitoring system, such things as internal coils, registers, timers and other items not visible externally can be monitored to determine proper operation. Also, internal register data can be altered if required to fine tune program operation. This can be advantageous when debugging the program. Communication with the programmable controller with this system is via a cable connected to a special programming port on the controller. Connection to the personal computer can be through a serial port or from a dedicated card installed in the computer.A Programmable Controller is a specialized computer. Since it is a computer, it has all the basic component parts that any other computer has; a Central Processing Unit, Memory, Input Interfacing and Output Interfacing.The Central Processing Unit (CPU) is the control portion of the PLC.It interprets the program commands retrieved from memory and acts onthose commands. In present day PLC's this unit is a microprocessor based system. The CPU is housed in the processor module of modularized systems.Memory in the system is generally of two types; ROM and RAM. The ROM memory contains the program information that allows the CPU to interpret and act on the Ladder Logic program stored in the RAM memory. RAM memoryis generally kept alive with an on-board battery so that ladder programming is not lost when the system power is removed. This batterycan be a standard dry cell or rechargeable nickel-cadmium type. NewerPLC units are now available with Electrically Erasable Programmable Read Only Memory (EEPROM) which does not require a battery. Memory is also housed in the processor module in modular systems.Input units can be any of several different types depending on input signals expected as described above. The input section can acceptdiscrete or analog signals of various voltage and current levels.Present day controllers offer discrete signal inputs of both AC and DC 第 5 页共7页voltages from TTL to 250 VDC and from 5 to 250 VAC. Analog inputunits can accept input levels such as ?10 VDC, ?5 VDC and 4-20 ma.current loop values. Discrete input units present each input to the CPUas a single 1 or 0 while analog input units contain analog to digital conversion circuitry and present the input voltage to the CPU as binary number normalized to the maximum count available from the unit. Thenumber of bits representing the input voltage or current depends uponthe resolution of the unit. This number generally contains a defined number of magnitude bits and a sign bit. Register input units presentthe word input to the CPU as it is received (Binary or BCD).Output units operate much the same as the input units with the exception that the unit is either sinking (supplying a ground) or sourcing (providing a voltage) discrete voltages or sourcing analog voltage or current. These output signals are presented as directed bythe CPU. The output circuit of discrete units can be transistors for TTL and higher DC voltage or Triacs for AC voltage outputs. For higher current applications and situations where a physical contact closure is required, mechanical relay contacts are available. These higher currents, however, are generally limited to about 2-3 amperes. The analog output units have internal circuitry which performs the digital to analog conversion and generates the variable voltage or current output.The first thing the PLC does when it begins to function is updateI/O. This means that all discrete input states are recorded from the input unit and all discrete states to be output are transferred to the output unit. Register data generally has specific addresses associated with it for both input and output data referred to as input and output registers. These registers are available to the input and output modules requiring them and are updated with the discrete data. Since this is input/output updating, it is referred to as I/O Update. The updating of discrete input and output information is accomplished with the use ofinput and output image registers set aside in the PLC memory. Each discrete input point has associated with it one bit of an input image register. Likewise, each discrete output point has one bit of an output image register associated with it. When I/O updating occurs, each input point that is ON at that time will cause a 1 to be set at the bit address associated with that particular input. If the input is off, a 0 will be set into the bit address. Memory in today's PLC's is generally 第 6 页共7页configured in 16 bit words. This means that one word of memory can store the states of 16 discrete input points. Therefore, there may be a number of words of memory set aside as the input and output image registers. At I/O update, the status of the input image register is set according to the state of all discrete inputs and the status of the output image register is transferred to the output unit. This transferof information typically only occurs at I/O update. It may be forced to occur at other times in PLC's which have an Immediate I/O Update command. This command will force the PLC to update the I/O at other timesalthough this would be a special case.Before a study of PLC programming can begin, it is important to gain a fundamental understanding of the various types of PLCs available, the advantages and disadvantages of each, and the way in which a PLC executes a program. The open frame, shoebox, and modular PLCs are each best suited to specific types of applications based on the environmental conditions, number of inputs and outputs, ease of expansion, and methodof entering and monitoring the program. Additionally, programming requires a prior knowledge of the manner in which a PLC receives input information, executes a program, and sends output information. With this information, we are now prepared to begin a study of PLC programming techniques.When writing programs for PLCs, it is beneficial to have a background in ladder diagramming for machine controls. This is basically the material that was covered in Chapter 1 of this text. The reason for this is that at a fundamental level, ladder logic programs for PLCs are very similar to electrical ladder diagrams. This is no coincidence.The engineers that developed the PLC programming language were sensitive to the fact that most engineers, technicians and electricians who work with electrical machines on a day-to-day basis will be familiar with this method of representing control logic. This would allow someone new to PLCs, but familiar with control diagrams, to be able to adapt very quickly to the programming language. It is likely that PLC programming language is one of the easiest programming languages to learn.第 7 页共7页可编程序控制器早期的机器用机械的方法采用凸轮控制、齿轮、杠杆和其他基本机械设备。
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附录Abstract: Programmable controller in the field of industrial control applications, and PLC in the application process, to ensure normal operation should be noted that a series of questions, and give some reasonable suggestions.Key words: PLC Industrial Control Interference Wiring Ground Proposal DescriptionOver the years, programmable logic controller (hereinafter referred to as PLC) from its production to the present, to achieve a connection to the storage logical leap of logic; its function from weak to strong, to achieve a logic control to digital control of progress; its applications from small to large, simple controls to achieve a single device to qualified motion control, process control and distributed control across the various tasks. PLC today in dealing with analog, digital computing, human-machine interface and the network have been a substantial increase in the capacity to become the mainstream of the field of control of industrial control equipment, in all walks of life playing an increasingly important role.ⅡPLC application areasCurrently, PLC has been widely used in domestic and foreign steel, petroleum, chemical, power, building materials, machinery manufacturing, automobile, textile, transportation, environmental and cultural entertainment and other industries, the use of mainly divided into the following categories:1. Binary logic controlReplace traditional relay circuit, logic control, sequential control, can be used to control a single device can also be used for multi-cluster control and automation lines. Such as injection molding machine, printing machine, stapler machine, lathe, grinding machines, packaging lines, plating lines and so on.2. Industrial Process ControlIn the industrial production process, there are some, such as temperature, pressure, flow, level and speed, the amount of continuous change (ie, analog), PLC using the appropriate A / D and D / A converter module, and a variety of control algorithm program to handle analog, complete closed-loop control. PID closed loop control system adjustment is generally used as a conditioning method was more. Process control in metallurgy, chemical industry, heat treatment, boiler control and so forth have a very wide range of applications3. Motion ControlPLC can be used in a circular motion or linear motion control. Generally use a dedicated motion control module, for example a stepper motor or servo motor driven single-axis or multi-axis position control module, used in a variety of machinery, machine tools, robots, elevators and other occasions.4. Data ProcessingPLC with mathematics (including matrix operations, functions, operation, logic operation), data transfer, data conversion, sorting, look-up table, bit manipulation functions, you can complete the data collection, analysis and processing. Dataprocessing is generally used, such as paper making, metallurgy, food industry, some of the major control system5. Communications and networkingPLC communication with the communication between PLC and the PLC and other communications between intelligent devices. Along with the development of factory automation network, the PLC now has communication interface, communication is very convenient.ⅢApplication features of PLC1. High reliability, strong anti-interferenceHigh reliability is the key to performance of electrical control equipment. PLC as the use of modern large scale integrated circuit technology, using the strict production process, the internal circuits to the advanced anti-jamming technology, with high reliability. Constitute a control system using PLC, and the same size compared to relay contactor system, electrical wiring and switch contacts have been reduced to hundreds or even thousands of times, fault also greatly reduced. In addition, PLC hardware failure with self-detection, failure alarm timely information. In the application software, application are also incorporated into the peripheral device fault diagnosis procedure, the system is in addition to PLC circuits and devices other than the access protection fault diagnosis. In this way, the whole system extremely high reliability.2. Fully furnished, fully functional, applicabilityPLC to today, has formed a series products of various sizes, can be used for occasions of all sizes of industrial control. In addition to processing other than logic, PLC data, most of computing power has improved, can be used for a variety of digital control in the field. A wide variety of functional units in large numbers, so that penetration to the position of PLC control, temperature control, CNC and other industrial control. Enhanced communication capabilities with PLC and human-machine interface technology, using the PLC control system composed of a variety of very easily.3. Easy to learn, well engineering and technical personnel welcomePLC is facing the industrial and mining enterprises in the industrial equipment. It interfaces easily, programming language easily acceptable for engineering and technical personnel. Ladder language, graphic symbols and expressions and relay circuit very close to are not familiar with electronic circuits, computer principles and assembly language do not understand people who engage in industrial control to open the door.4. System design, the workload is small, easy maintenance, easy to transformPLC logic with memory logic instead of wiring, greatly reducing the control equipment external wiring, make the control system design and construction of the much shorter period, while routine maintenance is also easier up, even more important is to change the procedures of the same equipment has been changed production process possible. This is particularly suitable for many varieties, small batch production situations.(1)Installation and wiring●Power lines, control lines and power lines and PLC I / O lines should be split wiring, isolation transformer and PLC and I / O should be used between the cable connection Shuangjiao. The PLC's IO lines and power lines go separate lines, such as to be in the same groove, the separation of bundled communication lines, DC lines, if conditions allow, the best sub-groove alignment, not only will it have the greatest possible distance and can reduce the noise to a minimum.●PLC should stay away from strong interference sources such as welding, high-power silicon rectifier devices and large power equipment, not with the high-voltage electrical switch installed in the same cabinet. PLC in the cabinet should stay away from power lines (the distance between the two should be more than 200mm). And PLC cabinets installed within the same inductive load, such as large power relay, contactor coil, arc should be parallel RC circuit.●PLC input and output separately from the best alignment, switch and analog should be laid separately. The transmission of analog signals should be shielded cable, one end or both ends of the shield should be grounding resistance should be less than the shielding layer 1 / 10.●AC output line and DC output lines do not use the same cable, the output line should be far from power lines and power lines, to avoid parallel.(2)I / O wiring terminalInput Connection●Input wiring generally not too long. But if the environment interfere with small, small voltage drop, the input terminal can be properly longer.●Input / output lines can not be used with a cable, input / output lines should be separated.●The extent possible, normally open contact form to connect to the input in the establishment of the ladder and relay the same schematic, easy to read。